An internal city fee-calculator microservice needs another service to run a named calculation as if calling a remote procedure and return a result. Which integration pattern best describes that interaction?

Remote procedure call (RPC) style integration presents remote operations as callable procedures that return results to the invoker. That differs from asynchronous file drops, unidirectional browser event streams, or informal messaging. Cloud+ covers RPC as one of the core system-integration patterns alongside REST, events, and other styles.