Returns a shard iterator. A shard iterator provides information about how to retrieve the stream records from within a shard. Use the shard iterator in a subsequent get_records request to read the stream records from the shard.
StreamArn: [required] The Amazon Resource Name (ARN) for the stream.
ShardId: [required] The identifier of the shard. The iterator will be returned for this shard ID.
ShardIteratorType: [required] Determines how the shard iterator is used to start reading stream records from the shard:
AT_SEQUENCE_NUMBER - Start reading exactly from the position denoted by a specific sequence number.
AFTER_SEQUENCE_NUMBER - Start reading right after the position denoted by a specific sequence number.
TRIM_HORIZON - Start reading at the last (untrimmed) stream record, which is the oldest record in the shard. In DynamoDB Streams, there is a 24 hour limit on data retention. Stream records whose age exceeds this limit are subject to removal (trimming) from the stream.
LATEST - Start reading just after the most recent stream record in the shard, so that you always read the most recent data in the shard.
SequenceNumber: The sequence number of a stream record in the shard from which to start reading.