The search API allows one to set the threading model the operation will be performed when the actual execution of the API is performed on the same node (the API is executed on a shard that is allocated on the same server).

There are three threading modes.The NO_THREADS mode means that the search operation will be executed on the calling thread. The SINGLE_THREAD mode means that the search operation will be executed on a single different thread for all local shards. The THREAD_PER_SHARD mode means that the search operation will be executed on a different thread for each local shard.

The default mode is THREAD_PER_SHARD.