We support query_binary, filter_binary and aggs_binary so a query, filter (post_filter actually) or aggregations can be provided in binary base64 format as part of the search request (plus other apis that support those sections).

This feature is undocumented and untested, at the point that we partially ended up removing it as part of the search refactoring (we currently don't parse query_binary anymore on the coordinating node).

I am opening this up for discussion, I never saw this feature used in real life, but maybe it is effectively used, anyways we should figure out whether we want to remove it or maintain it (then document it and test it too).