Solr has a HTTP/JSON-based API. However, it isn’t exactly a REST API because it doesn’t really follow any of the rules for a well-defined REST interface. I whine about this sometimes.

With the RESTful API, the user cannot directly set the number of wins, losses or ties. The client can only use a POST invocation to increment values one at a time. This is not an idempotent function, ...

The widespread use of ASCII encoding formats like JSON and rest may be killing server performance. A wide variety of emerging binary formats offer significantly improved performance for processing ...