What is Feast?

Feast (Feature Store) is a customizable operational data system that re-uses existing infrastructure to manage and serve machine learning features to realtime models.

Feast allows ML platform teams to:

• Make features consistently available for training and serving by managing an offline store (to process historical data for scale-out batch scoring or model training), a low-latency online store (to power real-time prediction), and a battle-tested feature server (to serve pre-computed features online).

• Avoid data leakage by generating point-in-time correct feature sets so data scientists can focus on feature engineering rather than debugging error-prone dataset joining logic. This ensure that future feature values do not leak to models during training.

• Decouple ML from data infrastructure by providing a single data access layer that abstracts feature storage from feature retrieval, ensuring models remain portable as you move from training models to serving models, from batch models to realtime models, and from one data infra system to another.

Who is Feast for?

Feast helps ML platform teams with DevOps experience productionize real-time models. Feast can also help these teams build towards a feature platform that improves collaboration between engineers and data scientists.

Feast is likely not the right tool if you

• are in an organization that’s just getting started with ML and is not yet sure what the business impact of ML is

• rely primarily on unstructured data

• need very low latency feature retrieval (e.g. p99 feature retrieval << 10ms)

• have a small team to support a large number of use cases

What Feast is not?

Feast is not

• a data warehouse: Feast is not a replacement for your data warehouse or the source of truth for all transformed data in your organization. Rather, Feast is a light-weight downstream layer that can serve data from an existing data warehouse (or other data sources) to models in production.

• a database: Feast is not a database, but helps manage data stored in other systems (e.g. BigQuery, Snowflake, DynamoDB, Redis) to make features consistently available at training / serving time

Feast does not fully solve

Example use cases

Many companies have used Feast to power real-world ML use cases such as:

• Personalizing online recommendations by leveraging pre-computed historical user or item features.

• Online fraud detection, using features that compare against (pre-computed) historical transaction patterns

• Churn prediction (an offline model), generating feature values for all users at a fixed cadence in batch

• Credit scoring, using pre-computed historical features to compute probability of default

How can I get started?

Explore the following resources to get started with Feast:

Links & Resources

• GitHub Repository: Find the complete Feast codebase on GitHub.

  • Community Governance Doc: See the governance model of Feast, including who the maintainers are and how decisions are made.

• Slack: Feel free to ask questions or say hello! This is the main place where maintainers and contributors brainstorm and where users ask questions or discuss best practices.

  • Feast users should join #feast-general or #feast-beginners to ask questions

  • Feast developers / contributors should join #feast-development

• Mailing list: We have both a user and developer mailing list.

  • Feast users should join feast-discuss@googlegroups.com group by clicking here.

  • Feast developers / contributors should join feast-dev@googlegroups.com group by clicking here.

• Community Calendar: Includes community calls and design meetings.

• Google Folder: This folder is used as a central repository for all Feast resources. For example:

  • Design proposals in the form of Request for Comments (RFC).

  • User surveys and meeting minutes.

  • Slide decks of conferences our contributors have spoken at.

• Feast Linux Foundation Wiki: Our LFAI wiki page contains links to resources for contributors and maintainers.

How can I get help?

• Slack: Need to speak to a human? Come ask a question in our Slack channel (link above).

• GitHub Issues: Found a bug or need a feature? Create an issue on GitHub.

• StackOverflow: Need to ask a question on how to use Feast? We also monitor and respond to StackOverflow.

Community Calls

General community call (biweekly)

We have a user and contributor community call every two weeks (US & EU friendly).

Frequency (every 2 weeks)

• Tuesday 10:00 am to 10:30 am PST

Links

• Zoom: https://zoom.us/j/6325193230

• Meeting notes (incl recordings): https://bit.ly/feast-notes

Developers call (biweekly)

We also have a #feast-development community call every two weeks, where we discuss contributions + brainstorm best practices.

Frequency (every 2 weeks)

• Tuesday 8:00 am to 8:30 am PST

Links

• Meeting notes (incl recordings): Feast Development Biweekly

• Zoom: https://zoom.us/j/93657748160?pwd=K3ZpdzhqejgrcXNhc3BlSjFMdzUxdz09

Feature views

A feature view is an object that represents a logical group of time-series feature data as it is found in a data source. Depending on the kind of feature view, it may contain some lightweight (experimental) feature transformations (see [Alpha] On demand feature views).

Feature views consist of:

• a data source

• zero or more entities

  • If the features are not related to a specific object, the feature view might not have entities; see feature views without entities below.

• a name to uniquely identify this feature view in the project.

• (optional, but recommended) a schema specifying one or more features (without this, Feast will infer the schema by reading from the data source)

• (optional, but recommended) metadata (for example, description, or other free-form metadata via tags)

• (optional) a TTL, which limits how far back Feast will look when generating historical datasets

Feature views allow Feast to model your existing feature data in a consistent way in both an offline (training) and online (serving) environment. Feature views generally contain features that are properties of a specific object, in which case that object is defined as an entity and included in the feature view.

from feast import BigQuerySource, Entity, FeatureView, Field
from feast.types import Float32, Int64

driver = Entity(name="driver", join_keys=["driver_id"])

driver_stats_fv = FeatureView(
    name="driver_activity",
    entities=[driver],
    schema=[
        Field(name="trips_today", dtype=Int64),
        Field(name="rating", dtype=Float32),
    ],
    source=BigQuerySource(
        table="feast-oss.demo_data.driver_activity"
    )
)

Feature views are used during

• The generation of training datasets by querying the data source of feature views in order to find historical feature values. A single training dataset may consist of features from multiple feature views.

• Loading of feature values into an online store. Feature views determine the storage schema in the online store. Feature values can be loaded from batch sources or from stream sources.

• Retrieval of features from the online store. Feature views provide the schema definition to Feast in order to look up features from the online store.

Feature views without entities

If a feature view contains features that are not related to a specific entity, the feature view can be defined without entities (only timestamps are needed for this feature view).

from feast import BigQuerySource, FeatureView, Field
from feast.types import Int64

global_stats_fv = FeatureView(
    name="global_stats",
    entities=[],
    schema=[
        Field(name="total_trips_today_by_all_drivers", dtype=Int64),
    ],
    source=BigQuerySource(
        table="feast-oss.demo_data.global_stats"
    )
)

Feature inferencing

If the schema parameter is not specified in the creation of the feature view, Feast will infer the features during feast apply by creating a Field for each column in the underlying data source except the columns corresponding to the entities of the feature view or the columns corresponding to the timestamp columns of the feature view's data source. The names and value types of the inferred features will use the names and data types of the columns from which the features were inferred.

Entity aliasing

"Entity aliases" can be specified to join entity_dataframe columns that do not match the column names in the source table of a FeatureView.

This could be used if a user has no control over these column names or if there are multiple entities are a subclass of a more general entity. For example, "spammer" and "reporter" could be aliases of a "user" entity, and "origin" and "destination" could be aliases of a "location" entity as shown below.

It is suggested that you dynamically specify the new FeatureView name using .with_name and join_key_map override using .with_join_key_map instead of needing to register each new copy.

from feast import BigQuerySource, Entity, FeatureView, Field
from feast.types import Int32, Int64

location = Entity(name="location", join_keys=["location_id"])

location_stats_fv= FeatureView(
    name="location_stats",
    entities=[location],
    schema=[
        Field(name="temperature", dtype=Int32),
        Field(name="location_id", dtype=Int64),
    ],
    source=BigQuerySource(
        table="feast-oss.demo_data.location_stats"
    ),
)

from location_stats_feature_view import location_stats_fv

temperatures_fs = FeatureService(
    name="temperatures",
    features=[
        location_stats_fv
            .with_name("origin_stats")
            .with_join_key_map(
                {"location_id": "origin_id"}
            ),
        location_stats_fv
            .with_name("destination_stats")
            .with_join_key_map(
                {"location_id": "destination_id"}
            ),
    ],
)

Field

A field or feature is an individual measurable property. It is typically a property observed on a specific entity, but does not have to be associated with an entity. For example, a feature of a customer entity could be the number of transactions they have made on an average month, while a feature that is not observed on a specific entity could be the total number of posts made by all users in the last month. Supported types for fields in Feast can be found in sdk/python/feast/types.py.

Fields are defined as part of feature views. Since Feast does not transform data, a field is essentially a schema that only contains a name and a type:

from feast import Field
from feast.types import Float32

trips_today = Field(
    name="trips_today",
    dtype=Float32
)

Together with data sources, they indicate to Feast where to find your feature values, e.g., in a specific parquet file or BigQuery table. Feature definitions are also used when reading features from the feature store, using feature references.

Feature names must be unique within a feature view.

Each field can have additional metadata associated with it, specified as key-value tags.

[Alpha] On demand feature views

On demand feature views allows data scientists to use existing features and request time data (features only available at request time) to transform and create new features. Users define python transformation logic which is executed in both the historical retrieval and online retrieval paths.

Currently, these transformations are executed locally. This is fine for online serving, but does not scale well to offline retrieval.

Why use on demand feature views?

This enables data scientists to easily impact the online feature retrieval path. For example, a data scientist could

1. Call get_historical_features to generate a training dataframe

2. Iterate in notebook on feature engineering in Pandas

3. Copy transformation logic into on demand feature views and commit to a dev branch of the feature repository

4. Verify with get_historical_features (on a small dataset) that the transformation gives expected output over historical data

5. Verify with get_online_features on dev branch that the transformation correctly outputs online features

6. Submit a pull request to the staging / prod branches which impact production traffic

from feast import Field, RequestSource
from feast.on_demand_feature_view import on_demand_feature_view
from feast.types import Float64

# Define a request data source which encodes features / information only
# available at request time (e.g. part of the user initiated HTTP request)
input_request = RequestSource(
    name="vals_to_add",
    schema=[
        Field(name="val_to_add", dtype=PrimitiveFeastType.INT64),
        Field(name="val_to_add_2": dtype=PrimitiveFeastType.INT64),
    ]
)

# Use the input data and feature view features to create new features
@on_demand_feature_view(
   sources=[
       driver_hourly_stats_view,
       input_request
   ],
   schema=[
     Field(name='conv_rate_plus_val1', dtype=Float64),
     Field(name='conv_rate_plus_val2', dtype=Float64)
   ]
)
def transformed_conv_rate(features_df: pd.DataFrame) -> pd.DataFrame:
    df = pd.DataFrame()
    df['conv_rate_plus_val1'] = (features_df['conv_rate'] + features_df['val_to_add'])
    df['conv_rate_plus_val2'] = (features_df['conv_rate'] + features_df['val_to_add_2'])
    return df

[Alpha] Stream feature views

A stream feature view is an extension of a normal feature view. The primary difference is that stream feature views have both stream and batch data sources, whereas a normal feature view only has a batch data source.

Stream feature views should be used instead of normal feature views when there are stream data sources (e.g. Kafka and Kinesis) available to provide fresh features in an online setting. Here is an example definition of a stream feature view with an attached transformation:

from datetime import timedelta

from feast import Field, FileSource, KafkaSource, stream_feature_view
from feast.data_format import JsonFormat
from feast.types import Float32

driver_stats_batch_source = FileSource(
    name="driver_stats_source",
    path="data/driver_stats.parquet",
    timestamp_field="event_timestamp",
)

driver_stats_stream_source = KafkaSource(
    name="driver_stats_stream",
    kafka_bootstrap_servers="localhost:9092",
    topic="drivers",
    timestamp_field="event_timestamp",
    batch_source=driver_stats_batch_source,
    message_format=JsonFormat(
        schema_json="driver_id integer, event_timestamp timestamp, conv_rate double, acc_rate double, created timestamp"
    ),
    watermark_delay_threshold=timedelta(minutes=5),
)

@stream_feature_view(
    entities=[driver],
    ttl=timedelta(seconds=8640000000),
    mode="spark",
    schema=[
        Field(name="conv_percentage", dtype=Float32),
        Field(name="acc_percentage", dtype=Float32),
    ],
    timestamp_field="event_timestamp",
    online=True,
    source=driver_stats_stream_source,
)
def driver_hourly_stats_stream(df: DataFrame):
    from pyspark.sql.functions import col

    return (
        df.withColumn("conv_percentage", col("conv_rate") * 100.0)
        .withColumn("acc_percentage", col("acc_rate") * 100.0)
        .drop("conv_rate", "acc_rate")
    )

See here for a example of how to use stream feature views to register your own streaming data pipelines in Feast.

In this tutorial we will

1. Deploy a local feature store with a Parquet file offline store and Sqlite online store.

2. Build a training dataset using our time series features from our Parquet files.

3. Ingest batch features ("materialization") and streaming features (via a Push API) into the online store.

4. Read the latest features from the offline store for batch scoring

5. Read the latest features from the online store for real-time inference.

6. Explore the (experimental) Feast UI

Overview

In this tutorial, we'll use Feast to generate training data and power online model inference for a ride-sharing driver satisfaction prediction model. Feast solves several common issues in this flow:

1. Training-serving skew and complex data joins: Feature values often exist across multiple tables. Joining these datasets can be complicated, slow, and error-prone.

   • Feast joins these tables with battle-tested logic that ensures point-in-time correctness so future feature values do not leak to models.

2. Online feature availability: At inference time, models often need access to features that aren't readily available and need to be precomputed from other data sources.

   • Feast manages deployment to a variety of online stores (e.g. DynamoDB, Redis, Google Cloud Datastore) and ensures necessary features are consistently available and freshly computed at inference time.

3. Feature and model versioning: Different teams within an organization are often unable to reuse features across projects, resulting in duplicate feature creation logic. Models have data dependencies that need to be versioned, for example when running A/B tests on model versions.

   • Feast enables discovery of and collaboration on previously used features and enables versioning of sets of features (via feature services).

   • (Experimental) Feast enables light-weight feature transformations so users can re-use transformation logic across online / offline use cases and across models.

Step 1: Install Feast

Install the Feast SDK and CLI using pip:

• In this tutorial, we focus on a local deployment. For a more in-depth guide on how to use Feast with Snowflake / GCP / AWS deployments, see Running Feast with Snowflake/GCP/AWS

pip install feast

Step 2: Create a feature repository

Bootstrap a new feature repository using feast init from the command line.

feast init my_project
cd my_project/feature_repo

Creating a new Feast repository in /home/Jovyan/my_project.

Let's take a look at the resulting demo repo itself. It breaks down into

• data/ contains raw demo parquet data

• example_repo.py contains demo feature definitions

• feature_store.yaml contains a demo setup configuring where data sources are

• test_workflow.py showcases how to run all key Feast commands, including defining, retrieving, and pushing features. You can run this with python test_workflow.py.

project: my_project
# By default, the registry is a file (but can be turned into a more scalable SQL-backed registry)
registry: data/registry.db
# The provider primarily specifies default offline / online stores & storing the registry in a given cloud
provider: local
online_store:
  type: sqlite
  path: data/online_store.db
entity_key_serialization_version: 2

# This is an example feature definition file

from datetime import timedelta

import pandas as pd

from feast import (
    Entity,
    FeatureService,
    FeatureView,
    Field,
    FileSource,
    PushSource,
    RequestSource,
)
from feast.on_demand_feature_view import on_demand_feature_view
from feast.types import Float32, Float64, Int64

# Define an entity for the driver. You can think of entity as a primary key used to
# fetch features.
driver = Entity(name="driver", join_keys=["driver_id"])

# Read data from parquet files. Parquet is convenient for local development mode. For
# production, you can use your favorite DWH, such as BigQuery. See Feast documentation
# for more info.
driver_stats_source = FileSource(
    name="driver_hourly_stats_source",
    path="%PARQUET_PATH%",
    timestamp_field="event_timestamp",
    created_timestamp_column="created",
)

# Our parquet files contain sample data that includes a driver_id column, timestamps and
# three feature column. Here we define a Feature View that will allow us to serve this
# data to our model online.
driver_stats_fv = FeatureView(
    # The unique name of this feature view. Two feature views in a single
    # project cannot have the same name
    name="driver_hourly_stats",
    entities=[driver],
    ttl=timedelta(days=1),
    # The list of features defined below act as a schema to both define features
    # for both materialization of features into a store, and are used as references
    # during retrieval for building a training dataset or serving features
    schema=[
        Field(name="conv_rate", dtype=Float32),
        Field(name="acc_rate", dtype=Float32),
        Field(name="avg_daily_trips", dtype=Int64),
    ],
    online=True,
    source=driver_stats_source,
    # Tags are user defined key/value pairs that are attached to each
    # feature view
    tags={"team": "driver_performance"},
)

# Defines a way to push data (to be available offline, online or both) into Feast.
driver_stats_push_source = PushSource(
    name="driver_stats_push_source",
    batch_source=driver_stats_source,
)

# Define a request data source which encodes features / information only
# available at request time (e.g. part of the user initiated HTTP request)
input_request = RequestSource(
    name="vals_to_add",
    schema=[
        Field(name="val_to_add", dtype=Int64),
        Field(name="val_to_add_2", dtype=Int64),
    ],
)


# Define an on demand feature view which can generate new features based on
# existing feature views and RequestSource features
@on_demand_feature_view(
    sources=[driver_stats_fv, input_request],
    schema=[
        Field(name="conv_rate_plus_val1", dtype=Float64),
        Field(name="conv_rate_plus_val2", dtype=Float64),
    ],
)
def transformed_conv_rate(inputs: pd.DataFrame) -> pd.DataFrame:
    df = pd.DataFrame()
    df["conv_rate_plus_val1"] = inputs["conv_rate"] + inputs["val_to_add"]
    df["conv_rate_plus_val2"] = inputs["conv_rate"] + inputs["val_to_add_2"]
    return df


# This groups features into a model version
driver_activity_v1 = FeatureService(
    name="driver_activity_v1",
    features=[
        driver_stats_fv[["conv_rate"]],  # Sub-selects a feature from a feature view
        transformed_conv_rate,  # Selects all features from the feature view
    ],
)
driver_activity_v2 = FeatureService(
    name="driver_activity_v2", features=[driver_stats_fv, transformed_conv_rate]
)

The feature_store.yaml file configures the key overall architecture of the feature store.

The provider value sets default offline and online stores.

• The offline store provides the compute layer to process historical data (for generating training data & feature values for serving).

• The online store is a low latency store of the latest feature values (for powering real-time inference).

Valid values for provider in feature_store.yaml are:

• local: use a SQL registry or local file registry. By default, use a file / Dask based offline store + SQLite online store

• gcp: use a SQL registry or GCS file registry. By default, use BigQuery (offline store) + Google Cloud Datastore (online store)

• aws: use a SQL registry or S3 file registry. By default, use Redshift (offline store) + DynamoDB (online store)

Note that there are many other offline / online stores Feast works with, including Spark, Azure, Hive, Trino, and PostgreSQL via community plugins. See Third party integrations for all supported data sources.

A custom setup can also be made by following Customizing Feast.

Inspecting the raw data

The raw feature data we have in this demo is stored in a local parquet file. The dataset captures hourly stats of a driver in a ride-sharing app.

import pandas as pd
pd.read_parquet("data/driver_stats.parquet")

Step 3: Run sample workflow

There's an included test_workflow.py file which runs through a full sample workflow:

1. Register feature definitions through feast apply

2. Generate a training dataset (using get_historical_features)

3. Generate features for batch scoring (using get_historical_features)

4. Ingest batch features into an online store (using materialize_incremental)

5. Fetch online features to power real time inference (using get_online_features)

6. Ingest streaming features into offline / online stores (using push)

7. Verify online features are updated / fresher

We'll walk through some snippets of code below and explain

Step 3a: Register feature definitions and deploy your feature store

The apply command scans python files in the current directory for feature view/entity definitions, registers the objects, and deploys infrastructure. In this example, it reads example_repo.py and sets up SQLite online store tables. Note that we had specified SQLite as the default online store by configuring online_store in feature_store.yaml.

feast apply

Created entity driver
Created feature view driver_hourly_stats
Created on demand feature view transformed_conv_rate
Created feature service driver_activity_v1
Created feature service driver_activity_v2

Created sqlite table my_project_driver_hourly_stats

Step 3b: Generating training data or powering batch scoring models

To train a model, we need features and labels. Often, this label data is stored separately (e.g. you have one table storing user survey results and another set of tables with feature values). Feast can help generate the features that map to these labels.

Feast needs a list of entities (e.g. driver ids) and timestamps. Feast will intelligently join relevant tables to create the relevant feature vectors. There are two ways to generate this list:

1. The user can query that table of labels with timestamps and pass that into Feast as an entity dataframe for training data generation.

2. The user can also query that table with a SQL query which pulls entities. See the documentation on feature retrieval for details

• Note that we include timestamps because we want the features for the same driver at various timestamps to be used in a model.

Generating training data

from datetime import datetime
import pandas as pd

from feast import FeatureStore

# Note: see https://docs.feast.dev/getting-started/concepts/feature-retrieval for 
# more details on how to retrieve for all entities in the offline store instead
entity_df = pd.DataFrame.from_dict(
    {
        # entity's join key -> entity values
        "driver_id": [1001, 1002, 1003],
        # "event_timestamp" (reserved key) -> timestamps
        "event_timestamp": [
            datetime(2021, 4, 12, 10, 59, 42),
            datetime(2021, 4, 12, 8, 12, 10),
            datetime(2021, 4, 12, 16, 40, 26),
        ],
        # (optional) label name -> label values. Feast does not process these
        "label_driver_reported_satisfaction": [1, 5, 3],
        # values we're using for an on-demand transformation
        "val_to_add": [1, 2, 3],
        "val_to_add_2": [10, 20, 30],
    }
)

store = FeatureStore(repo_path=".")

training_df = store.get_historical_features(
    entity_df=entity_df,
    features=[
        "driver_hourly_stats:conv_rate",
        "driver_hourly_stats:acc_rate",
        "driver_hourly_stats:avg_daily_trips",
        "transformed_conv_rate:conv_rate_plus_val1",
        "transformed_conv_rate:conv_rate_plus_val2",
    ],
).to_df()

print("----- Feature schema -----\n")
print(training_df.info())

print()
print("----- Example features -----\n")
print(training_df.head())

----- Feature schema -----

<class 'pandas.core.frame.DataFrame'>
Int64Index: 3 entries, 0 to 2
Data columns (total 6 columns):
 #   Column                              Non-Null Count  Dtype
---  ------                              --------------  -----
 0   event_timestamp                     3 non-null      datetime64[ns, UTC]
 1   driver_id                           3 non-null      int64
 2   label_driver_reported_satisfaction  3 non-null      int64
 3   conv_rate                           3 non-null      float32
 4   acc_rate                            3 non-null      float32
 5   avg_daily_trips                     3 non-null      int32
dtypes: datetime64[ns, UTC](1), float32(2), int32(1), int64(2)
memory usage: 132.0 bytes
None

----- Example features -----

                   event_timestamp  driver_id  ...  acc_rate  avg_daily_trips
0 2021-08-23 15:12:55.489091+00:00       1003  ...  0.077863              741
1 2021-08-23 15:49:55.489089+00:00       1002  ...  0.074327              113
2 2021-08-23 16:14:55.489075+00:00       1001  ...  0.105046              347

[3 rows x 6 columns]

Run offline inference (batch scoring)

To power a batch model, we primarily need to generate features with the get_historical_features call, but using the current timestamp

entity_df["event_timestamp"] = pd.to_datetime("now", utc=True)
training_df = store.get_historical_features(
    entity_df=entity_df,
    features=[
        "driver_hourly_stats:conv_rate",
        "driver_hourly_stats:acc_rate",
        "driver_hourly_stats:avg_daily_trips",
        "transformed_conv_rate:conv_rate_plus_val1",
        "transformed_conv_rate:conv_rate_plus_val2",
    ],
).to_df()

print("\n----- Example features -----\n")
print(training_df.head())

----- Example features -----

   driver_id                  event_timestamp  ... acc_rate  avg_daily_trips  conv_rate_plus_val1  
0       1001 2022-08-08 18:22:06.555018+00:00  ... 0.864639              359             1.663844
1       1002 2022-08-08 18:22:06.555018+00:00  ... 0.695982              311             2.151189 
2       1003 2022-08-08 18:22:06.555018+00:00  ... 0.949191              789             3.769165 

Step 3c: Ingest batch features into your online store

We now serialize the latest values of features since the beginning of time to prepare for serving (note: materialize-incremental serializes all new features since the last materialize call).

CURRENT_TIME=$(date -u +"%Y-%m-%dT%H:%M:%S")
feast materialize-incremental $CURRENT_TIME

Materializing 1 feature views to 2021-08-23 16:25:46+00:00 into the sqlite online
store.

driver_hourly_stats from 2021-08-22 16:25:47+00:00 to 2021-08-23 16:25:46+00:00:
100%|████████████████████████████████████████████| 5/5 [00:00<00:00, 592.05it/s]

Step 3d: Fetching feature vectors for inference

At inference time, we need to quickly read the latest feature values for different drivers (which otherwise might have existed only in batch sources) from the online feature store using get_online_features(). These feature vectors can then be fed to the model.

from pprint import pprint
from feast import FeatureStore

store = FeatureStore(repo_path=".")

feature_vector = store.get_online_features(
    features=[
        "driver_hourly_stats:conv_rate",
        "driver_hourly_stats:acc_rate",
        "driver_hourly_stats:avg_daily_trips",
    ],
    entity_rows=[
        # {join_key: entity_value}
        {"driver_id": 1004},
        {"driver_id": 1005},
    ],
).to_dict()

pprint(feature_vector)

{
 'acc_rate': [0.5732735991477966, 0.7828438878059387],
 'avg_daily_trips': [33, 984],
 'conv_rate': [0.15498852729797363, 0.6263588070869446],
 'driver_id': [1004, 1005]
}

Step 3e: Using a feature service to fetch online features instead.

You can also use feature services to manage multiple features, and decouple feature view definitions and the features needed by end applications. The feature store can also be used to fetch either online or historical features using the same API below. More information can be found here.

The driver_activity_v1 feature service pulls all features from the driver_hourly_stats feature view:

from feast import FeatureService
driver_stats_fs = FeatureService(
    name="driver_activity_v1", features=[driver_hourly_stats_view]
)

from pprint import pprint
from feast import FeatureStore
feature_store = FeatureStore('.')  # Initialize the feature store

feature_service = feature_store.get_feature_service("driver_activity_v1")
feature_vector = feature_store.get_online_features(
    features=feature_service,
    entity_rows=[
        # {join_key: entity_value}
        {"driver_id": 1004},
        {"driver_id": 1005},
    ],
).to_dict()
pprint(feature_vector)

{
 'acc_rate': [0.5732735991477966, 0.7828438878059387],
 'avg_daily_trips': [33, 984],
 'conv_rate': [0.15498852729797363, 0.6263588070869446],
 'driver_id': [1004, 1005]
}

Step 4: Browse your features with the Web UI (experimental)

View all registered features, data sources, entities, and feature services with the Web UI.

One of the ways to view this is with the feast ui command.

feast ui

INFO:     Started server process [66664]
08/17/2022 01:25:49 PM uvicorn.error INFO: Started server process [66664]
INFO:     Waiting for application startup.
08/17/2022 01:25:49 PM uvicorn.error INFO: Waiting for application startup.
INFO:     Application startup complete.
08/17/2022 01:25:49 PM uvicorn.error INFO: Application startup complete.
INFO:     Uvicorn running on http://0.0.0.0:8888 (Press CTRL+C to quit)
08/17/2022 01:25:49 PM uvicorn.error INFO: Uvicorn running on http://0.0.0.0:8888 (Press CTRL+C to quit)

Step 5: Re-examine test_workflow.py

Take a look at test_workflow.py again. It showcases many sample flows on how to interact with Feast. You'll see these show up in the upcoming concepts + architecture + tutorial pages as well.

Next steps

• Join the email newsletter to get new updates on Feast / feature stores.

• Read the Concepts page to understand the Feast data model.

• Read the Architecture page.

• Check out our Tutorials section for more examples on how to use Feast.

• Follow our Running Feast with Snowflake/GCP/AWS guide for a more in-depth tutorial on using Feast.

• Join other Feast users and contributors in Slack and become part of the community!

Feast project structure

The top-level namespace within Feast is a project. Users define one or more feature views within a project. Each feature view contains one or more features. These features typically relate to one or more entities. A feature view must always have a data source, which in turn is used during the generation of training datasets and when materializing feature values into the online store.

Projects provide complete isolation of feature stores at the infrastructure level. This is accomplished through resource namespacing, e.g., prefixing table names with the associated project. Each project should be considered a completely separate universe of entities and features. It is not possible to retrieve features from multiple projects in a single request. We recommend having a single feature store and a single project per environment (dev, staging, prod).

Data ingestion

For offline use cases that only rely on batch data, Feast does not need to ingest data and can query your existing data (leveraging a compute engine, whether it be a data warehouse or (experimental) Spark / Trino). Feast can help manage pushing streaming features to a batch source to make features available for training.

For online use cases, Feast supports ingesting features from batch sources to make them available online (through a process called materialization), and pushing streaming features to make them available both offline / online. We explore this more in the next concept page (Data ingestion)

Feature registration and retrieval

Features are registered as code in a version controlled repository, and tie to data sources + model versions via the concepts of entities, feature views, and feature services. We explore these concepts more in the upcoming concept pages. These features are then stored in a registry, which can be accessed across users and services. The features can then be retrieved via SDK API methods or via a deployed feature server which exposes endpoints to query for online features (to power real time models).

Feast supports several patterns of feature retrieval.

Feature values in Feast are modeled as time-series records. Below is an example of a driver feature view with two feature columns (trips_today, and earnings_today):

The above table can be registered with Feast through the following feature view:

Feast is able to join features from one or more feature views onto an entity dataframe in a point-in-time correct way. This means Feast is able to reproduce the state of features at a specific point in the past.

Given the following entity dataframe, imagine a user would like to join the above driver_hourly_stats feature view onto it, while preserving the trip_success column:

The timestamps within the entity dataframe above are the events at which we want to reproduce the state of the world (i.e., what the feature values were at those specific points in time). In order to do a point-in-time join, a user would load the entity dataframe and run historical retrieval:

For each row within the entity dataframe, Feast will query and join the selected features from the appropriate feature view data source. Feast will scan backward in time from the entity dataframe timestamp up to a maximum of the TTL time specified.

Below is the resulting joined training dataframe. It contains both the original entity rows and joined feature values:

Three feature rows were successfully joined to the entity dataframe rows. The first row in the entity dataframe was older than the earliest feature rows in the feature view and could not be joined. The last row in the entity dataframe was outside of the TTL window (the event happened 11 hours after the feature row) and also couldn't be joined.

An entity is a collection of semantically related features. Users define entities to map to the domain of their use case. For example, a ride-hailing service could have customers and drivers as their entities, which group related features that correspond to these customers and drivers.

The entity name is used to uniquely identify the entity (for example to show in the experimental Web UI). The join key is used to identify the physical primary key on which feature values should be joined together to be retrieved during feature retrieval.

Entities are used by Feast in many contexts, as we explore below:

Use case #1: Defining and storing features

Feast's primary object for defining features is a feature view, which is a collection of features. Feature views map to 0 or more entities, since a feature can be associated with:

• zero entities (e.g. a global feature like num_daily_global_transactions)

• one entity (e.g. a user feature like user_age or last_5_bought_items)

• multiple entities, aka a composite key (e.g. a user + merchant category feature like num_user_purchases_in_merchant_category)

Feast refers to this collection of entities for a feature view as an entity key.

Entities should be reused across feature views. This helps with discovery of features, since it enables data scientists understand how other teams build features for the entity they are most interested in.

Feast will use the feature view concept to then define the schema of groups of features in a low-latency online store.

Use case #2: Retrieving features

At serving time, users specify entity key(s) to fetch the latest feature values which can power real-time model prediction (e.g. a fraud detection model that needs to fetch the latest transaction user's features to make a prediction).

Data source

A data source in Feast refers to raw underlying data that users own (e.g. in a table in BigQuery). Feast does not manage any of the raw underlying data but instead, is in charge of loading this data and performing different operations on the data to retrieve or serve features.

Feast uses a time-series data model to represent data. This data model is used to interpret feature data in data sources in order to build training datasets or materialize features into an online store.

Below is an example data source with a single entity column (driver) and two feature columns (trips_today, and rating).

Feast supports primarily time-stamped tabular data as data sources. There are many kinds of possible data sources:

• Batch data sources: ideally, these live in data warehouses (BigQuery, Snowflake, Redshift), but can be in data lakes (S3, GCS, etc). Feast supports ingesting and querying data across both.

• Stream data sources: Feast does not have native streaming integrations. It does however facilitate making streaming features available in different environments. There are two kinds of sources:

  • Push sources allow users to push features into Feast, and make it available for training / batch scoring ("offline"), for realtime feature serving ("online") or both.

  • [Alpha] Stream sources allow users to register metadata from Kafka or Kinesis sources. The onus is on the user to ingest from these sources, though Feast provides some limited helper methods to ingest directly from Kafka / Kinesis topics.

Batch data ingestion

Ingesting from batch sources is only necessary to power real-time models. This is done through materialization. Under the hood, Feast manages an offline store (to scalably generate training data from batch sources) and an online store (to provide low-latency access to features for real-time models).

A key command to use in Feast is the materialize_incremental command, which fetches the latest values for all entities in the batch source and ingests these values into the online store.

Materialization can be called programmatically or through the CLI:

Batch data schema inference

If the schema parameter is not specified when defining a data source, Feast attempts to infer the schema of the data source during feast apply. The way it does this depends on the implementation of the offline store. For the offline stores that ship with Feast out of the box this inference is performed by inspecting the schema of the table in the cloud data warehouse, or if a query is provided to the source, by running the query with a LIMIT clause and inspecting the result.

Stream data ingestion

Ingesting from stream sources happens either via a Push API or via a contrib processor that leverages an existing Spark context.

Feast uses a registry to store all applied Feast objects (e.g. Feature views, entities, etc). The registry exposes methods to apply, list, retrieve and delete these objects, and is an abstraction with multiple implementations.

Options for registry implementations

File-based registry

By default, Feast uses a file-based registry implementation, which stores the protobuf representation of the registry as a serialized file. This registry file can be stored in a local file system, or in cloud storage (in, say, S3 or GCS, or Azure).

The quickstart guides that use feast init will use a registry on a local file system. To allow Feast to configure a remote file registry, you need to create a GCS / S3 bucket that Feast can understand:

However, there are inherent limitations with a file-based registry, since changing a single field in the registry requires re-writing the whole registry file. With multiple concurrent writers, this presents a risk of data loss, or bottlenecks writes to the registry since all changes have to be serialized (e.g. when running materialization for multiple feature views or time ranges concurrently).

SQL Registry

The configuration roughly looks like:

Updating the registry

Accessing the registry from clients

Users can specify the registry through a feature_store.yaml config file, or programmatically. We often see teams preferring the programmatic approach because it makes notebook driven development very easy:

Option 1: programmatically specifying the registry

Option 2: specifying the registry in the project's feature_store.yaml file

Instantiating a FeatureStore object can then point to this:

The list below contains the functionality that contributors are planning to develop for Feast.

• We welcome contribution to all items in the roadmap!

• Have questions about the roadmap? Go to the Slack channel to ask on #feast-development.

• Data Sources
• Offline Stores
• Online Stores
• Feature Engineering
• Streaming
• Deployments
• Feature Serving

  • Python Client
• • Data profiling and validation (Great Expectations)

• Feature Discovery and Governance

  • Python SDK for browsing feature registry

  • CLI for browsing feature registry

  • Model-centric feature tracking (feature services)

Overview

Generally, Feast supports several patterns of feature retrieval:

1. Training data generation (via feature_store.get_historical_features(...))

2. Offline feature retrieval for batch scoring (via feature_store.get_historical_features(...))

3. Online feature retrieval for real-time model predictions

   • via the SDK: feature_store.get_online_features(...)

   • via deployed feature server endpoints: requests.post('http://localhost:6566/get-online-features', data=json.dumps(online_request))

Each of these retrieval mechanisms accept:

• some way of specifying entities (to fetch features for)

• some way to specify the features to fetch (either via feature services, which group features needed for a model version, or feature references)

Before beginning, you need to instantiate a local FeatureStore object that knows how to parse the registry (see more details)

For code examples of how the below work, inspect the generated repository from feast init -t [YOUR TEMPLATE] (gcp, snowflake, and aws are the most fully fleshed).

Concepts

Before diving into how to retrieve features, we need to understand some high level concepts in Feast.

Feature Services

A feature service is an object that represents a logical group of features from one or more feature views. Feature Services allows features from within a feature view to be used as needed by an ML model. Users can expect to create one feature service per model version, allowing for tracking of the features used by models.

from driver_ratings_feature_view import driver_ratings_fv
from driver_trips_feature_view import driver_stats_fv

driver_stats_fs = FeatureService(
    name="driver_activity",
    features=[driver_stats_fv, driver_ratings_fv[["lifetime_rating"]]]
)

Feature services are used during

• The generation of training datasets when querying feature views in order to find historical feature values. A single training dataset may consist of features from multiple feature views.

• Retrieval of features for batch scoring from the offline store (e.g. with an entity dataframe where all timestamps are now())

• Retrieval of features from the online store for online inference (with smaller batch sizes). The features retrieved from the online store may also belong to multiple feature views.

Feature services enable referencing all or some features from a feature view.

Retrieving from the online store with a feature service

from feast import FeatureStore
feature_store = FeatureStore('.')  # Initialize the feature store

feature_service = feature_store.get_feature_service("driver_activity")
features = feature_store.get_online_features(
    features=feature_service, entity_rows=[entity_dict]
)

Retrieving from the offline store with a feature service

from feast import FeatureStore
feature_store = FeatureStore('.')  # Initialize the feature store

feature_service = feature_store.get_feature_service("driver_activity")
feature_store.get_historical_features(features=feature_service, entity_df=entity_df)

Feature References

This mechanism of retrieving features is only recommended as you're experimenting. Once you want to launch experiments or serve models, feature services are recommended.

Feature references uniquely identify feature values in Feast. The structure of a feature reference in string form is as follows: <feature_view>:<feature>

Feature references are used for the retrieval of features from Feast:

online_features = fs.get_online_features(
    features=[
        'driver_locations:lon',
        'drivers_activity:trips_today'
    ],
    entity_rows=[
        # {join_key: entity_value}
        {'driver': 'driver_1001'}
    ]
)

It is possible to retrieve features from multiple feature views with a single request, and Feast is able to join features from multiple tables in order to build a training dataset. However, it is not possible to reference (or retrieve) features from multiple projects at the same time.

Event timestamp

The timestamp on which an event occurred, as found in a feature view's data source. The event timestamp describes the event time at which a feature was observed or generated.

Event timestamps are used during point-in-time joins to ensure that the latest feature values are joined from feature views onto entity rows. Event timestamps are also used to ensure that old feature values aren't served to models during online serving.

Dataset

A dataset is a collection of rows that is produced by a historical retrieval from Feast in order to train a model. A dataset is produced by a join from one or more feature views onto an entity dataframe. Therefore, a dataset may consist of features from multiple feature views.

Dataset vs Feature View: Feature views contain the schema of data and a reference to where data can be found (through its data source). Datasets are the actual data manifestation of querying those data sources.

Dataset vs Data Source: Datasets are the output of historical retrieval, whereas data sources are the inputs. One or more data sources can be used in the creation of a dataset.

Retrieving historical features (for training data or batch scoring)

Feast abstracts away point-in-time join complexities with the get_historical_features API.

We go through the major steps, and also show example code. Note that the quickstart templates generally have end-to-end working examples for all these cases.

entity_df = pd.DataFrame.from_dict(
    {
        "driver_id": [1001, 1002, 1003, 1004, 1001],
        "event_timestamp": [
            datetime(2021, 4, 12, 10, 59, 42),
            datetime(2021, 4, 12, 8, 12, 10),
            datetime(2021, 4, 12, 16, 40, 26),
            datetime(2021, 4, 12, 15, 1, 12),
            datetime.now()
        ]
    }
)
training_df = store.get_historical_features(
    entity_df=entity_df,
    features=store.get_feature_service("model_v1"),
).to_df()
print(training_df.head())

from feast import FeatureStore

store = FeatureStore(repo_path=".")

# Get the latest feature values for unique entities
entity_sql = f"""
    SELECT
        driver_id,
        CURRENT_TIMESTAMP() as event_timestamp
    FROM {store.get_data_source("driver_hourly_stats_source").get_table_query_string()}
    WHERE event_timestamp BETWEEN '2021-01-01' and '2021-12-31'
    GROUP BY driver_id
"""
batch_scoring_features = store.get_historical_features(
    entity_df=entity_sql,
    features=store.get_feature_service("model_v2"),
).to_df()
# predictions = model.predict(batch_scoring_features)

Step 1: Specifying Features

Feast accepts either:

• feature services, which group features needed for a model version

• feature references

Example: querying a feature service (recommended)

training_df = store.get_historical_features(
    entity_df=entity_df,
    features=store.get_feature_service("model_v1"),
).to_df()

Example: querying a list of feature references

training_df = store.get_historical_features(
    entity_df=entity_df,
    features=[
        "driver_hourly_stats:conv_rate",
        "driver_hourly_stats:acc_rate",
        "driver_daily_features:daily_miles_driven"
    ],
).to_df()

Step 2: Specifying Entities

Feast accepts either a Pandas dataframe as the entity dataframe (including entity keys and timestamps) or a SQL query to generate the entities.

Both approaches must specify the full entity key needed as well as the timestamps. Feast then joins features onto this dataframe.

Example: entity dataframe for generating training data

entity_df = pd.DataFrame.from_dict(
    {
        "driver_id": [1001, 1002, 1003, 1004, 1001],
        "event_timestamp": [
            datetime(2021, 4, 12, 10, 59, 42),
            datetime(2021, 4, 12, 8, 12, 10),
            datetime(2021, 4, 12, 16, 40, 26),
            datetime(2021, 4, 12, 15, 1, 12),
            datetime.now()
        ]
    }
)
training_df = store.get_historical_features(
    entity_df=entity_df,
    features=[
        "driver_hourly_stats:conv_rate",
        "driver_hourly_stats:acc_rate",
        "driver_daily_features:daily_miles_driven"
    ],
).to_df()

Example: entity SQL query for generating training data

You can also pass a SQL string to generate the above dataframe. This is useful for getting all entities in a timeframe from some data source.

entity_sql = f"""
    SELECT
        driver_id,
        event_timestamp
    FROM {store.get_data_source("driver_hourly_stats_source").get_table_query_string()}
    WHERE event_timestamp BETWEEN '2021-01-01' and '2021-12-31'
"""
training_df = store.get_historical_features(
    entity_df=entity_sql,
    features=[
        "driver_hourly_stats:conv_rate",
        "driver_hourly_stats:acc_rate",
        "driver_daily_features:daily_miles_driven"
    ],
).to_df()

Retrieving online features (for model inference)

Feast will ensure the latest feature values for registered features are available. At retrieval time, you need to supply a list of entities and the corresponding features to be retrieved. Similar to get_historical_features, we recommend using feature services as a mechanism for grouping features in a model version.

Note: unlike get_historical_features, the entity_rows do not need timestamps since you only want one feature value per entity key.

There are several options for retrieving online features: through the SDK, or through a feature server

from feast import RepoConfig, FeatureStore
from feast.repo_config import RegistryConfig

repo_config = RepoConfig(
    registry=RegistryConfig(path="gs://feast-test-gcs-bucket/registry.pb"),
    project="feast_demo_gcp",
    provider="gcp",
)
store = FeatureStore(config=repo_config)

features = store.get_online_features(
    features=[
        "driver_hourly_stats:conv_rate",
        "driver_hourly_stats:acc_rate",
        "driver_daily_features:daily_miles_driven",
    ],
    entity_rows=[
        {
            "driver_id": 1001,
        }
    ],
).to_dict()

import requests
import json

online_request = {
    "features": [
        "driver_hourly_stats:conv_rate",
    ],
    "entities": {"driver_id": [1001, 1002]},
}
r = requests.post('http://localhost:6566/get-online-features', data=json.dumps(online_request))
print(json.dumps(r.json(), indent=4, sort_keys=True))

An offline store is an interface for working with historical time-series feature values that are stored in data sources. The OfflineStore interface has several different implementations, such as the BigQueryOfflineStore, each of which is backed by a different storage and compute engine. For more details on which offline stores are supported, please see Offline Stores.

Offline stores are primarily used for two reasons:

1. Building training datasets from time-series features.

2. Materializing (loading) features into an online store to serve those features at low-latency in a production setting.

Offline stores are configured through the feature_store.yaml. When building training datasets or materializing features into an online store, Feast will use the configured offline store with your configured data sources to execute the necessary data operations.

Only a single offline store can be used at a time. Moreover, offline stores are not compatible with all data sources; for example, the BigQuery offline store cannot be used to query a file-based data source.

Please see Push Source for more details on how to push features directly to the offline store in your feature store.

The Feast feature registry is a central catalog of all the feature definitions and their related metadata. It allows data scientists to search, discover, and collaborate on new features.

Each Feast deployment has a single feature registry. Feast only supports file-based registries today, but supports four different backends.

• Local: Used as a local backend for storing the registry during development

• S3: Used as a centralized backend for storing the registry on AWS

• GCS: Used as a centralized backend for storing the registry on GCP

• [Alpha] Azure: Used as centralized backend for storing the registry on Azure Blob storage.

The feature registry is updated during different operations when using Feast. More specifically, objects within the registry (entities, feature views, feature services) are updated when running apply from the Feast CLI, but metadata about objects can also be updated during operations like materialization.

Users interact with a feature registry through the Feast SDK. Listing all feature views:

fs = FeatureStore("my_feature_repo/")
print(fs.list_feature_views())

Or retrieving a specific feature view:

fs = FeatureStore("my_feature_repo/")
fv = fs.get_feature_view(“my_fv1”)

Feast datasets allow for conveniently saving dataframes that include both features and entities to be subsequently used for data analysis and model training. Data Quality Monitoring was the primary motivation for creating dataset concept.

Dataset's metadata is stored in the Feast registry and raw data (features, entities, additional input keys and timestamp) is stored in the offline store.

Dataset can be created from:

1. Results of historical retrieval

2. [planned] Logging request (including input for on demand transformation) and response during feature serving

3. [planned] Logging features during writing to online store (from batch source or stream)

Creating a saved dataset from historical retrieval

To create a saved dataset from historical features for later retrieval or analysis, a user needs to call get_historical_features method first and then pass the returned retrieval job to create_saved_dataset method. create_saved_dataset will trigger the provided retrieval job (by calling .persist() on it) to store the data using the specified storage behind the scenes. Storage type must be the same as the globally configured offline store (e.g it's impossible to persist data to a different offline source). create_saved_dataset will also create a SavedDataset object with all of the related metadata and will write this object to the registry.

from feast import FeatureStore
from feast.infra.offline_stores.bigquery_source import SavedDatasetBigQueryStorage

store = FeatureStore()

historical_job = store.get_historical_features(
    features=["driver:avg_trip"],
    entity_df=...,
)

dataset = store.create_saved_dataset(
    from_=historical_job,
    name='my_training_dataset',
    storage=SavedDatasetBigQueryStorage(table_ref='<gcp-project>.<gcp-dataset>.my_training_dataset'),
    tags={'author': 'oleksii'}
)

dataset.to_df()

Saved dataset can be retrieved later using the get_saved_dataset method in the feature store:

dataset = store.get_saved_dataset('my_training_dataset')
dataset.to_df()

Check out our tutorial on validating historical features to see how this concept can be applied in a real-world use case.

Feast uses online stores to serve features at low latency. Feature values are loaded from data sources into the online store through materialization, which can be triggered through the materialize command.

The storage schema of features within the online store mirrors that of the original data source. One key difference is that for each entity key, only the latest feature values are stored. No historical values are stored.

Here is an example batch data source:

Once the above data source is materialized into Feast (using feast materialize), the feature values will be stored as follows:

Features can also be written directly to the online store via push sources .

Getting started

Do you have any examples of how Feast should be used?

Concepts

Do feature views have to include entities?

How does Feast handle model or feature versioning?

Feast expects that each version of a model corresponds to a different feature service.

Feature views once they are used by a feature service are intended to be immutable and not deleted (until a feature service is removed). In the future, feast plan and feast apply will throw errors if it sees this kind of behavior.

What is the difference between data sources and the offline store?

Is it possible to have offline and online stores from different providers?

Yes, this is possible. For example, you can use BigQuery as an offline store and Redis as an online store.

Functionality

How do I run get_historical_features without providing an entity dataframe?

Does Feast provide security or access control?

Feast currently does not support any access control other than the access control required for the Provider's environment (for example, GCP and AWS permissions).

It is a good idea though to lock down the registry file so only the CI/CD pipeline can modify it. That way data scientists and other users cannot accidentally modify the registry and lose other team's data.

Does Feast support streaming sources?

Does Feast support feature transformation?

There are several kinds of transformations:

• • These transformations are Pandas transformations run on batch data when you call get_historical_features and at online serving time when you call `get_online_features.

  • Note that if you use push sources to ingest streaming features, these transformations will execute on the fly as well

• • These will include SQL + PySpark based transformations on batch data sources.

• Streaming transformations (RFC in progress)

Does Feast have a Web UI?

Does Feast support composite keys?

A feature view can be defined with multiple entities. Since each entity has a unique join_key, using multiple entities will achieve the effect of a composite key.

How does Feast compare with Tecton?

What are the performance/latency characteristics of Feast?

Does Feast support embeddings and list features?

Yes. Specifically:

• Simple lists / dense embeddings:

  • BigQuery supports list types natively

  • Redshift does not support list types, so you'll need to serialize these features into strings (e.g. json or protocol buffers)
• Sparse embeddings (e.g. one hot encodings)

Does Feast support X storage engine?

Does Feast support using different clouds for offline vs online stores?

Yes. Using a GCP or AWS provider in feature_store.yaml primarily sets default offline / online stores and configures where the remote registry file can live (Using the AWS provider also allows for deployment to AWS Lambda). You can override the offline and online stores to be in different clouds if you wish.

What is the difference between a data source and an offline store?

The data source and the offline store are closely tied, but separate concepts. The offline store controls how feast talks to a data store for historical feature retrieval, and the data source points to specific table (or query) within a data store. Offline stores are infrastructure-level connectors to data stores like Snowflake.

Additional differences:

• Data sources may be specific to a project (e.g. feed ranking), but offline stores are agnostic and used across projects.

• A feast project may define several data sources that power different feature views, but a feast project has a single offline store.

• Feast users typically need to define data sources when using feast, but only need to use/configure existing offline stores without creating new ones.

How can I add a custom online store?

Can the same storage engine be used for both the offline and online store?

Yes. For example, the Postgres connector can be used as both an offline and online store (as well as the registry).

Does Feast support S3 as a data source?

Yes. There are two ways to use S3 in Feast:

• Using the s3_endpoint_override in a FileSource data source. This endpoint is more suitable for quick proof of concepts that won't necessarily scale for production use cases.

Is Feast planning on supporting X functionality?

Project

How do I contribute to Feast?

Feast 0.9 (legacy)

What is the difference between Feast 0.9 and Feast 0.10+?

How do I migrate from Feast 0.9 to Feast 0.10+?

What are the plans for Feast Core, Feast Serving, and Feast Spark?

In this example, you'll learn how to use some of the key functionality in Feast. The tutorial runs in both local mode and on the Google Cloud Platform (GCP). For GCP, you must have access to a GCP project already, including read and write permissions to BigQuery.

Try it and let us know what you think!

These Feast tutorials showcase how to use Feast to simplify end to end model training / serving.

We integrate with a wide set of tools and technologies so you can make Feast work in your existing stack. Many of these integrations are maintained as plugins to the main Feast repo.

Integrations

Standards

In order for a plugin integration to be highlighted, it must meet the following requirements:

2. The plugin must have some basic documentation on how it should be used.

3. The author must work with a maintainer to pass a basic code review (e.g. to ensure that the implementation roughly matches the core Feast implementations).

In order for a plugin integration to be merged into the main Feast repo, it must meet the following requirements:

1. The PR must pass all integration tests. The universal tests (tests specifically designed for custom integrations) must be updated to test the integration.

2. There is documentation and a tutorial on how to use the integration.

3. The author (or someone else) agrees to take ownership of all the files, and maintain those files going forward.

4. If the plugin is being contributed by an organization, and not an individual, the organization should provide the infrastructure (or credits) for integration tests.

A provider is an implementation of a feature store using specific feature store components (e.g. offline store, online store) targeting a specific environment (e.g. GCP stack).

Providers orchestrate various components (offline store, online store, infrastructure, compute) inside an environment. For example, the gcp provider supports BigQuery as an offline store and Datastore as an online store, ensuring that these components can work together seamlessly. Feast has three built-in providers (local, gcp, and aws) with default configurations that make it easy for users to start a feature store in a specific environment. These default configurations can be overridden easily. For instance, you can use the gcp provider but use Redis as the online store instead of Datastore.

If the built-in providers are not sufficient, you can create your own custom provider. Please see this guide for more details.

Please see feature_store.yaml for configuring providers.

When individuals apply for loans from banks and other credit providers, the decision to approve a loan application is often made through a statistical model. This model uses information about a customer to determine the likelihood that they will repay or default on a loan, in a process called credit scoring.

In this example, we will demonstrate how a real-time credit scoring system can be built using Feast and Scikit-Learn on AWS, using feature data from S3.

This real-time system accepts a loan request from a customer and responds within 100ms with a decision on whether their loan has been approved or rejected.

Real-time Credit Scoring Example

This end-to-end tutorial will take you through the following steps:

• Deploying S3 with Parquet as your primary data source, containing both loan features and zip code features

• Deploying Redshift as the interface Feast uses to build training datasets

• Registering your features with Feast and configuring DynamoDB for online serving

• Building a training dataset with Feast to train your credit scoring model

• Loading feature values from S3 into DynamoDB

• Making online predictions with your credit scoring model using features from DynamoDB

Throughout this tutorial, we’ll walk through the creation of a production-ready fraud prediction system. A prediction is made in real-time as the user makes the transaction, so we need to be able to generate a prediction at low latency.

Fraud Detection Example

Our end-to-end example will perform the following workflows:

• Computing and backfilling feature data from raw data

• Building point-in-time correct training datasets from feature data and training a model

• Making online predictions from feature data

Here's a high-level picture of our system architecture on Google Cloud Platform (GCP):

Install Feast using pip:

pip install feast

Install Feast with Snowflake dependencies (required when using Snowflake):

pip install 'feast[snowflake]'

Install Feast with GCP dependencies (required when using BigQuery or Firestore):

pip install 'feast[gcp]'

Install Feast with AWS dependencies (required when using Redshift or DynamoDB):

pip install 'feast[aws]'

Install Feast with Redis dependencies (required when using Redis, either through AWS Elasticache or independently):

pip install 'feast[redis]'

A feature repository is a directory that contains the configuration of the feature store and individual features. This configuration is written as code (Python/YAML) and it's highly recommended that teams track it centrally using git. See Feature Repository for a detailed explanation of feature repositories.

The easiest way to create a new feature repository to use feast init command:

feast init

Creating a new Feast repository in /<...>/tiny_pika.

feast init -t snowflake
Snowflake Deployment URL: ...
Snowflake User Name: ...
Snowflake Password: ...
Snowflake Role Name: ...
Snowflake Warehouse Name: ...
Snowflake Database Name: ...

Creating a new Feast repository in /<...>/tiny_pika.

feast init -t gcp

Creating a new Feast repository in /<...>/tiny_pika.

feast init -t aws
AWS Region (e.g. us-west-2): ...
Redshift Cluster ID: ...
Redshift Database Name: ...
Redshift User Name: ...
Redshift S3 Staging Location (s3://*): ...
Redshift IAM Role for S3 (arn:aws:iam::*:role/*): ...
Should I upload example data to Redshift (overwriting 'feast_driver_hourly_stats' table)? (Y/n):

Creating a new Feast repository in /<...>/tiny_pika.

The init command creates a Python file with feature definitions, sample data, and a Feast configuration file for local development:

$ tree
.
└── tiny_pika
    ├── data
    │   └── driver_stats.parquet
    ├── example.py
    └── feature_store.yaml

1 directory, 3 files

Enter the directory:

# Replace "tiny_pika" with your auto-generated dir name
cd tiny_pika

You can now use this feature repository for development. You can try the following:

• Run feast apply to apply these definitions to Feast.

• Edit the example feature definitions in example.py and run feast apply again to change feature definitions.

• Initialize a git repository in the same directory and checking the feature repository into version control.

Overview

Feast is designed to be easy to use and understand out of the box, with as few infrastructure dependencies as possible. However, there are components used by default that may not scale well. Since Feast is designed to be modular, it's possible to swap such components with more performant components, at the cost of Feast depending on additional infrastructure.

Scaling Feast Registry

The default Feast registry is a file-based registry. Any changes to the feature repo, or materializing data into the online store, results in a mutation to the registry.

However, there are inherent limitations with a file-based registry, since changing a single field in the registry requires re-writing the whole registry file. With multiple concurrent writers, this presents a risk of data loss, or bottlenecks writes to the registry since all changes have to be serialized (e.g. when running materialization for multiple feature views or time ranges concurrently).

The recommended solution in this case is to use the SQL based registry, which allows concurrent, transactional, and fine-grained updates to the registry. This registry implementation requires access to an existing database (such as MySQL, Postgres, etc).

Scaling Materialization

The default Feast materialization process is an in-memory process, which pulls data from the offline store before writing it to the online store. However, this process does not scale for large data sets, since it's executed on a single-process.

Feast supports pluggable Materialization Engines, that allow the materialization process to be scaled up. Aside from the local process, Feast supports a Lambda-based materialization engine, and a Bytewax-based materialization engine.

Users may also be able to build an engine to scale up materialization using existing infrastructure in their organizations.

Feast allows users to load their feature data into an online store in order to serve the latest features to models for online prediction.

Materializing features

1. Register feature views

Before proceeding, please ensure that you have applied (registered) the feature views that should be materialized.

2.a Materialize

The materialize command allows users to materialize features over a specific historical time range into the online store.

feast materialize 2021-04-07T00:00:00 2021-04-08T00:00:00

The above command will query the batch sources for all feature views over the provided time range, and load the latest feature values into the configured online store.

It is also possible to materialize for specific feature views by using the -v / --views argument.

feast materialize 2021-04-07T00:00:00 2021-04-08T00:00:00 \
--views driver_hourly_stats

The materialize command is completely stateless. It requires the user to provide the time ranges that will be loaded into the online store. This command is best used from a scheduler that tracks state, like Airflow.

2.b Materialize Incremental (Alternative)

For simplicity, Feast also provides a materialize command that will only ingest new data that has arrived in the offline store. Unlike materialize, materialize-incremental will track the state of previous ingestion runs inside of the feature registry.

The example command below will load only new data that has arrived for each feature view up to the end date and time (2021-04-08T00:00:00).

feast materialize-incremental 2021-04-08T00:00:00

The materialize-incremental command functions similarly to materialize in that it loads data over a specific time range for all feature views (or the selected feature views) into the online store.

Unlike materialize, materialize-incremental automatically determines the start time from which to load features from batch sources of each feature view. The first time materialize-incremental is executed it will set the start time to the oldest timestamp of each data source, and the end time as the one provided by the user. For each run of materialize-incremental, the end timestamp will be tracked.

Subsequent runs of materialize-incremental will then set the start time to the end time of the previous run, thus only loading new data that has arrived into the online store. Note that the end time that is tracked for each run is at the feature view level, not globally for all feature views, i.e, different feature views may have different periods that have been materialized into the online store.

Overview

By default, the registry Feast uses a file-based registry implementation, which stores the protobuf representation of the registry as a serialized file. This registry file can be stored in a local file system, or in cloud storage (in, say, S3 or GCS).

However, there's inherent limitations with a file-based registry, since changing a single field in the registry requires re-writing the whole registry file. With multiple concurrent writers, this presents a risk of data loss, or bottlenecks writes to the registry since all changes have to be serialized (e.g. when running materialization for multiple feature views or time ranges concurrently).

• PostgreSQL

• MySQL

• Sqlite

Feast can use the SQL Registry via a config change in the feature_store.yaml file. An example of how to configure this would be:

Should you choose to use a database technology that is compatible with one of Feast's supported registry backends, but which speaks a different dialect (e.g. cockroachdb, which is compatible with postgres) then some further intervention may be required on your part.

Psycopg2, which is the database library leveraged by the online and offline stores, is not impacted by the need to speak a particular dialect, and so the following only applies to the registry.

If you are not running Feast in a container, to accomodate SQLAlchemy's need to speak an external dialect, install additional Python modules like we do as follows using cockroachdb for example:

If you are running Feast in a container, you will need to create a custom image like we do as follows, again using cockroachdb as an example:

If you are running Feast in Kubernetes, set the image.repository and imagePullSecrets Helm values accordingly to utilize your custom image.

There are some things to note about how the SQL registry works:

• Once instantiated, the Registry ensures the tables needed to store data exist, and creates them if they do not.

• Upon tearing down the feast project, the registry ensures that the tables are dropped from the database.

• The schema for how data is laid out in tables can be found . It is intentionally simple, storing the serialized protobuf versions of each Feast object keyed by its name.

Example Usage: Concurrent materialization

The SQL Registry should be used when materializing feature views concurrently to ensure correctness of data in the registry. This can be achieved by simply running feast materialize or feature_store.materialize multiple times using a correctly configured feature_store.yaml. This will make each materialization process talk to the registry database concurrently, and ensure the metadata updates are serialized.

Feast allows users to build a training dataset from time-series feature data that already exists in an offline store. Users are expected to provide a list of features to retrieve (which may span multiple feature views), and a dataframe to join the resulting features onto. Feast will then execute a point-in-time join of multiple feature views onto the provided dataframe, and return the full resulting dataframe.

Retrieving historical features

1. Register your feature views

Please ensure that you have created a feature repository and that you have registered (applied) your feature views with Feast.

2. Define feature references

Start by defining the feature references (e.g., driver_trips:average_daily_rides) for the features that you would like to retrieve from the offline store. These features can come from multiple feature tables. The only requirement is that the feature tables that make up the feature references have the same entity (or composite entity), and that they aren't located in the same offline store.

3. Create an entity dataframe

An entity dataframe is the target dataframe on which you would like to join feature values. The entity dataframe must contain a timestamp column called event_timestamp and all entities (primary keys) necessary to join feature tables onto. All entities found in feature views that are being joined onto the entity dataframe must be found as column on the entity dataframe.

It is possible to provide entity dataframes as either a Pandas dataframe or a SQL query.

Pandas:

In the example below we create a Pandas based entity dataframe that has a single row with an event_timestamp column and a driver_id entity column. Pandas based entity dataframes may need to be uploaded into an offline store, which may result in longer wait times compared to a SQL based entity dataframe.

SQL (Alternative):

Below is an example of an entity dataframe built from a BigQuery SQL query. It is only possible to use this query when all feature views being queried are available in the same offline store (BigQuery).

4. Launch historical retrieval

Once the feature references and an entity dataframe are defined, it is possible to call get_historical_features(). This method launches a job that executes a point-in-time join of features from the offline store onto the entity dataframe. Once completed, a job reference will be returned. This job reference can then be converted to a Pandas dataframe by calling to_df().

Feast supports registering streaming feature views and Kafka and Kinesis streaming sources. It also provides an interface for stream processing called the Stream Processor. An example Kafka/Spark StreamProcessor is implemented in the contrib folder. For more details, please see the RFC for more details.

Please see here for a tutorial on how to build a versioned streaming pipeline that registers your transformations, features, and data sources in Feast.

Feast is highly pluggable and configurable:

• One can use existing plugins (offline store, online store, batch materialization engine, providers) and configure those using the built in options. See reference documentation for details.

• The other way to customize Feast is to build your own custom components, and then point Feast to delegate to them.

Below are some guides on how to add new custom components:

A batch materialization engine is a component of Feast that's responsible for moving data from the offline store into the online store.

A materialization engine abstracts over specific technologies or frameworks that are used to materialize data. It allows users to use a pure local serialized approach (which is the default LocalMaterializationEngine), or delegates the materialization to seperate components (e.g. AWS Lambda, as implemented by the the LambdaMaterializaionEngine).

Overview

Feast batch materialization operations (materialize and materialize-incremental) execute through a BatchMaterializationEngine.

Custom batch materialization engines allow Feast users to extend Feast to customize the materialization process. Examples include:

• Setting up custom materialization-specific infrastructure during feast apply (e.g. setting up Spark clusters or Lambda Functions)

• Launching custom batch ingestion (materialization) jobs (Spark, Beam, AWS Lambda)

• Tearing down custom materialization-specific infrastructure during feast teardown (e.g. tearing down Spark clusters, or deleting Lambda Functions)

Guide

The fastest way to add custom logic to Feast is to extend an existing materialization engine. The most generic engine is the LocalMaterializationEngine which contains no cloud-specific logic. The guide that follows will extend the LocalProvider with operations that print text to the console. It is up to you as a developer to add your custom code to the engine methods, but the guide below will provide the necessary scaffolding to get you started.

Step 1: Define an Engine class

The first step is to define a custom materialization engine class. We've created the MyCustomEngine below.

Notice how in the above engine we have only overwritten two of the methods on the LocalMaterializatinEngine, namely update and materialize. These two methods are convenient to replace if you are planning to launch custom batch jobs.

Step 2: Configuring Feast to use the engine

Notice how the batch_engine field above points to the module and class where your engine can be found.

Step 3: Using the engine

Now you should be able to use your engine by running a Feast command:

It may also be necessary to add the module root path to your PYTHONPATH as follows:

That's it. You should now have a fully functional custom engine!