Register a Kinesis enhanced fan-out consumer with RegisterStreamConsumer and manage per-shard subscriptions via SubscribeToShard

Steps

1. Call RegisterStreamConsumer with the stream ARN and a unique consumer name; the response includes a ConsumerARN — wait until DescribeStreamConsumer shows ConsumerStatus=ACTIVE before subscribing
2. For each shard, call SubscribeToShard with the ConsumerARN and shard ID; provide a StartingPosition specifying AT_LATEST, AT_TIMESTAMP, AT_SEQUENCE_NUMBER, or AFTER_SEQUENCE_NUMBER
3. Process the streaming HTTP/2 response: each SubscribeToShard call returns a 5-minute streaming session delivering records via server-sent events at up to 2 MB/s per shard dedicated throughput
4. Renew subscriptions before the 5-minute session expires by issuing a new SubscribeToShard call on the same shard; use the ContinuationSequenceNumber from the last received record as the new starting position
5. Handle shard splits and merges: when a shard is split, SubscribeToShard on the parent returns an event indicating it is closed; call ListShards to discover the two child shards and subscribe to each
6. Monitor consumer-level metrics: GetShardIterator is not used for enhanced fan-out — RegisterStreamConsumer has a limit of 5 calls per second per account; consumer limit is 20 per stream by default, or 50 for accounts with On-demand Advantage