Backend-for-Frontend and Client-Specific API Design Questions

Shaping API responses to the needs of specific client types: the Backend-for-Frontend (BFF) pattern, one BFF per client versus a shared gateway, client-side composition or a generic API, what belongs in a BFF (including normalizing inconsistent downstream pagination and error formats for one client), and aggregating several backend calls into one client-shaped response. Covers payload shaping (sparse fieldsets and field selection against relational and document stores, partial responses, optional expansion of related collections, delta responses with deletions, compact serialization including binary wire formats), round-trip reduction and composite views for feeds and dashboards, adapting to mobile versus web bandwidth, battery and device constraints (device-appropriate image variants, prefetching and refresh frequency tuned to connection quality), and choosing GraphQL versus REST to fix over- and under-fetching, including incremental migration from REST to GraphQL. Authentication, general REST resource design, versioning, rate limiting, offline sync and real-time transport are covered elsewhere.