The recommendation-api is currently exposed through RESTbase at /api/rest_v1/data/recommendation/. To unblock RESTbase sunsetting, it needs to be exposed through the new REST Gateway (Envoy). Before we can switch routing, the service's needs should be assessed according to https://www.mediawiki.org/wiki/RESTBase/service_migration, and necessary work sheduled.
This appears to be used by the Wikipedia app at a rate of about one request per second: https://w.wiki/ASXp