<p>Merges two adjacent shards in a Kinesis data stream and combines them into a single shard to reduce the stream's capacity to ingest and transport data. This API is only supported for the data streams with the provisioned capacity mode. Two shards are considered adjacent if the union of the hash key ranges for the two shards form a contiguous set with no gaps. For example, if you have two shards, one with a hash key range of 276...381 and the other with a hash key range of 382...454, then you could merge these two shards into a single shard that would have a hash key range of 276...454. After the merge, the single child shard receives data for all hash key values covered by the two parent shards.</p> <note> <p>When invoking this API, it is recommended you use the <code>StreamARN</code> input parameter rather than the <code>StreamName</code> input parameter.</p> </note> <p> <code>MergeShards</code> is called when there is a need to reduce the overall capacity of a stream because of excess capacity that is not being used. You must specify the shard to be merged and the adjacent shard for a stream. For more information about merging shards, see <a href="https://docs.aws.amazon.com/kinesis/latest/dev/kinesis-using-sdk-java-resharding-merge.html">Merge Two Shards</a> in the <i>Amazon Kinesis Data Streams Developer Guide</i>.</p> <p>If the stream is in the <code>ACTIVE</code> state, you can call <code>MergeShards</code>. If a stream is in the <code>CREATING</code>, <code>UPDATING</code>, or <code>DELETING</code> state, <code>MergeShards</code> returns a <code>ResourceInUseException</code>. If the specified stream does not exist, <code>MergeShards</code> returns a <code>ResourceNotFoundException</code>. </p> <p>You can use <a>DescribeStreamSummary</a> to check the state of the stream, which is returned in <code>StreamStatus</code>.</p> <p> <code>MergeShards</code> is an asynchronous operation. Upon receiving a <code>MergeShards</code> request, Amazon Kinesis Data Streams immediately returns a response and sets the <code>StreamStatus</code> to <code>UPDATING</code>. After the operation is completed, Kinesis Data Streams sets the <code>StreamStatus</code> to <code>ACTIVE</code>. Read and write operations continue to work while the stream is in the <code>UPDATING</code> state. </p> <p>You use <a>DescribeStreamSummary</a> and the <a>ListShards</a> APIs to determine the shard IDs that are specified in the <code>MergeShards</code> request. </p> <p>If you try to operate on too many streams in parallel using <a>CreateStream</a>, <a>DeleteStream</a>, <code>MergeShards</code>, or <a>SplitShard</a>, you receive a <code>LimitExceededException</code>. </p> <p> <code>MergeShards</code> has a limit of five transactions per second per account.</p>

{
  "success": true,
  "data": {
    "id": "abc123",
    "created_at": "2025-01-01T00:00:00Z"
  }
}

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid request parameters"
  }
}