overview.md

Overview

Functionality

Here are the methods exposed by the OnlineStore interface, along with the core functionality supported by the method:

• online_write_batch: write feature values to the online store
• online_read: read feature values from the online store
• update: update infrastructure (e.g. tables) in the online store
• teardown: teardown infrastructure (e.g. tables) in the online store
• plan: generate a plan of infrastructure changes based on feature repo changes

There is also additional functionality not properly captured by these interface methods:

• support for on-demand transforms
• readable by Python SDK
• readable by Java
• readable by Go
• support for entityless feature views
• support for concurrent writing to the same key
• support for ttl (time to live) at retrieval
• support for deleting expired data

Finally, there are multiple data models for storing the features in the online store. For example, features could be:

• collocated by feature view
• collocated by feature service
• collocated by entity key

See this issue for a discussion around the tradeoffs of each of these data models.

Functionality Matrix

There are currently five core online store implementations: SqliteOnlineStore, RedisOnlineStore, DynamoDBOnlineStore, SnowflakeOnlineStore, and DatastoreOnlineStore. There are several additional implementations contributed by the Feast community (PostgreSQLOnlineStore, HbaseOnlineStore, CassandraOnlineStore and IKVOnlineStore), which are not guaranteed to be stable or to match the functionality of the core implementations. Details for each specific online store, such as how to configure it in a feature_store.yaml, can be found here.

Below is a matrix indicating which online stores support what functionality.

	Sqlite	Redis	DynamoDB	Snowflake	Datastore	Postgres	Hbase	[Cassandra / Astra DB]	IKV
write feature values to the online store	yes	yes	yes	yes	yes	yes	yes	yes	yes
read feature values from the online store	yes	yes	yes	yes	yes	yes	yes	yes	yes
update infrastructure (e.g. tables) in the online store	yes	yes	yes	yes	yes	yes	yes	yes	yes
teardown infrastructure (e.g. tables) in the online store	yes	yes	yes	yes	yes	yes	yes	yes	yes
generate a plan of infrastructure changes	yes	no	no	no	no	no	no	yes	no
support for on-demand transforms	yes	yes	yes	yes	yes	yes	yes	yes	yes
readable by Python SDK	yes	yes	yes	yes	yes	yes	yes	yes	yes
readable by Java	no	yes	no	no	no	no	no	no	no
readable by Go	yes	yes	no	no	no	no	no	no	no
support for entityless feature views	yes	yes	yes	yes	yes	yes	yes	yes	yes
support for concurrent writing to the same key	no	yes	no	no	no	no	no	no	yes
support for ttl (time to live) at retrieval	no	yes	no	no	no	no	no	no	no
support for deleting expired data	no	yes	no	no	no	no	no	no	no
collocated by feature view	yes	no	yes	yes	yes	yes	yes	yes	no
collocated by feature service	no	no	no	no	no	no	no	no	no
collocated by entity key	no	yes	no	no	no	no	no	no	yes