Method and system for processing read queries in an application programming interface based on declarative schemas for individual services

Certain aspects of the present disclosure provide techniques for processing east-west queries in an application programming interface (API) generated for a plurality of associated services. The method generally includes receiving, at a request gateway from a requesting service, a request to invoke a function exposed by a first service through the API. References to entities defined in a declarative schema for one or more second services are identified based on identifiers included a record retrieved from a data repository for an entity returned by the function. A message is published on a message bus to the one or more second services to retrieve information related to the referenced entities. A response message including objects associated with the referenced entities is consumed. The function is executed based on the objects associated with the referenced entities, and the result generated by executing the function is returned to the requesting service.