This operation establishes an HTTP/2 connection between the consumer you specify in the ConsumerARN parameter and the shard you specify in the ShardId parameter. After the connection is successfully established, Kinesis Data Streams pushes records from the shard to the consumer over this connection. Before you call this operation, call RegisterStreamConsumer to register the consumer with Kinesis Data Streams.

When the SubscribeToShard call succeeds, your consumer starts receiving events of type SubscribeToShardEvent over the HTTP/2 connection for up to 5 minutes, after which time you need to call SubscribeToShard again to renew the subscription if you want to continue to receive records.

You can make one call to SubscribeToShard per second per registered consumer per shard. For example, if you have a 4000 shard stream and two registered stream consumers, you can make one SubscribeToShard request per second for each combination of shard and registered consumer, allowing you to subscribe both consumers to all 4000 shards in one second.

If you call SubscribeToShard again with the same ConsumerARN and ShardId within 5 seconds of a successful call, you'll get a ResourceInUseException. If you call SubscribeToShard 5 seconds or more after a successful call, the second call takes over the subscription and the previous connection expires or fails with a ResourceInUseException.

For an example of how to use this operations, see Enhanced Fan-Out Using the Kinesis Data Streams API.