How does Rails handle large-scale API composition and aggregation layers?

Rails uses backend-for-frontend (BFF) layers to aggregate multiple microservice APIs into unified responses.

API composition involves combining responses from multiple services into a single API response optimized for client needs. Rails often acts as a BFF layer that orchestrates calls to user, order, and notification services. Performance concerns include parallelization, caching, and failure isolation. This reduces frontend complexity but can introduce backend bottlenecks if not carefully designed.