Similar to the Bulk API, Elasticsearch provides you with a way to gather multiple search (_msearch) requests together to send out in a batch. You need to put the header and the corresponding request body as a pair in the multi-search request body. You can specify the appropriate index names and parameters in the header, including search_type, preference, and routing. The header content type must be set to the newline delimited JSON format (application/x-ndjson).
Now, let's look at an example to issue an _msearch request that contains two sub-requests to find those EFTs in the cf_etf and cf_view indices that do not have the rating field. In the following screenshot, you can see that the response body has a responses field with the array type that contains two results corresponding to the two sub-requests:
