> For the complete documentation index, see [llms.txt](https://docs.feast.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.feast.dev/v0.22-branch/getting-started/concepts/stream-feature-view.md).

# Stream feature view

## 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:

```python
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](https://github.com/feast-dev/streaming-tutorial) for a example of how to use stream feature views.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.feast.dev/v0.22-branch/getting-started/concepts/stream-feature-view.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.