# MongoDB ## Description The [MongoDB](https://www.mongodb.com/) online store provides support for materializing feature values into MongoDB for serving online features. {% hint style="warning" %} The MongoDB online store is currently in **preview**. Some functionality may be unstable, and breaking changes may occur in future releases. {% endhint %} ## Features * Supports both synchronous and asynchronous operations for high-performance feature retrieval * Native async support uses PyMongo's `AsyncMongoClient` (no Motor dependency required) * Flexible connection options supporting MongoDB Atlas, self-hosted MongoDB, and MongoDB replica sets * Automatic index creation for optimized query performance * Entity key collocation for efficient feature retrieval ## Getting started In order to use this online store, you'll need to install the MongoDB extra (along with the dependency needed for the offline store of choice): ```bash pip install 'feast[mongodb]' ``` You can get started by using any of the other templates (e.g. `feast init -t gcp` or `feast init -t snowflake` or `feast init -t aws`), and then swapping in MongoDB as the online store as seen below in the examples. ## Examples ### Basic configuration with MongoDB Atlas {% code title="feature\_store.yaml" %} ```yaml project: my_feature_repo registry: data/registry.db provider: local online_store: type: mongodb connection_string: "mongodb+srv://username:password@cluster.mongodb.net/" # pragma: allowlist secret database_name: feast_online_store ``` {% endcode %} ### Self-hosted MongoDB with authentication {% code title="feature\_store.yaml" %} ```yaml project: my_feature_repo registry: data/registry.db provider: local online_store: type: mongodb connection_string: "mongodb://username:password@localhost:27017/" # pragma: allowlist secret database_name: feast_online_store collection_suffix: features ``` {% endcode %} ### MongoDB replica set configuration {% code title="feature\_store.yaml" %} ```yaml project: my_feature_repo registry: data/registry.db provider: local online_store: type: mongodb connection_string: "mongodb://host1:27017,host2:27017,host3:27017/?replicaSet=myReplicaSet" database_name: feast_online_store client_kwargs: retryWrites: true w: majority ``` {% endcode %} ### Advanced configuration with custom client options {% code title="feature\_store.yaml" %} ```yaml project: my_feature_repo registry: data/registry.db provider: local online_store: type: mongodb connection_string: "mongodb+srv://cluster.mongodb.net/" database_name: feast_online_store collection_suffix: features client_kwargs: maxPoolSize: 50 minPoolSize: 10 serverSelectionTimeoutMS: 5000 connectTimeoutMS: 10000 ``` {% endcode %} The full set of configuration options is available in [MongoDBOnlineStoreConfig](https://rtd.feast.dev/en/latest/#feast.infra.online_stores.mongodb_online_store.mongodb.MongoDBOnlineStoreConfig). ## Data Model The MongoDB online store uses a **single collection per project** with entity key collocation. Features from multiple feature views for the same entity are stored together in a single document. ### Example Document Schema The example shows a single entity. It contains 3 features from 2 feature views: "rating" and "trips\_last7d" from Feature View "driver\_stats", and "surge\_multiplier" from "pricing" view. Each feature view has its own event timestamp. The "created\_timestamp" marks when the entity was materialized. ```javascript { "_id": "", // Binary entity key (bytes) "features": { "driver_stats": { "rating": 4.91, "trips_last_7d": 132 }, "pricing": { "surge_multiplier": 1.2 } }, "event_timestamps": { "driver_stats": ISODate("2026-01-20T12:00:00Z"), "pricing": ISODate("2026-01-21T08:30:00Z") }, "created_timestamp": ISODate("2026-01-21T12:00:05Z") } ``` ### Key Design Decisions * **`_id` field**: Uses the serialized entity key (bytes) as the primary key for efficient lookups * **Nested features**: Features are organized by feature view name, allowing multiple feature views per entity * **Event timestamps**: Stored per feature view to track when each feature set was last updated * **Created timestamp**: Global timestamp for the entire document ### Indexes The online store automatically creates the following index: * Primary key index on `_id` (automatic in MongoDB), set to the serialized entity key. No additional indexes are required for the online store operations. ## Async Support The MongoDB online store provides native async support using PyMongo 4.13+'s stable `AsyncMongoClient`. This enables: * **High concurrency**: Handle thousands of concurrent feature requests without thread pool limitations * **True async I/O**: Non-blocking operations for better performance in async applications * **10-20x performance improvement**: For concurrent workloads compared to sequential sync operations Both sync and async methods are fully supported: * `online_read` / `online_read_async` * `online_write_batch` / `online_write_batch_async` ## Functionality Matrix The set of functionality supported by online stores is described in detail [here](https://docs.feast.dev/master/reference/overview#functionality). Below is a matrix indicating which functionality is supported by the MongoDB online store. | | MongoDB | | --------------------------------------------------------- | ------- | | write feature values to the online store | yes | | read feature values from the online store | yes | | update infrastructure (e.g. tables) in the online store | yes | | teardown infrastructure (e.g. tables) in the online store | yes | | generate a plan of infrastructure changes | no | | support for on-demand transforms | yes | | readable by Python SDK | yes | | readable by Java | no | | readable by Go | no | | support for entityless feature views | yes | | support for concurrent writing to the same key | yes | | support for ttl (time to live) at retrieval | no | | support for deleting expired data | no | | collocated by feature view | no | | collocated by feature service | no | | collocated by entity key | yes | To compare this set of functionality against other online stores, please see the full [functionality matrix](https://docs.feast.dev/master/reference/overview#functionality-matrix).