tl;dr: RFC 10008 defines QUERY, a new HTTP method that combines GET's safety and idempotency with POST's ability to send request bodies, solving the problem of queries too large to fit in a URL. Responses are cacheable (with the cache key derived from request content), and servers can optionally return Location or Content-Location headers pointing to equivalent GET-able resources for the query or its results. A companion Accept-Query response header advertises which media types a resource supports for queries.