The Elasticsearch REST APIs are exposed over HTTP.
A number of Elasticsearch GET APIs—most notably the search API—support a request body.
While the GET action makes sense in the context of retrieving information,
GET requests with a body are not supported by all HTTP libraries.
All Elasticsearch GET APIs that require a body can also be submitted as POST requests.
Alternatively, you can pass the request body as the
source query string parameter
when using GET.