When should I use a Backend for Frontend instead of an API gateway?

Use a Backend for Frontend (BFF) when the backend needs to be optimized for a specific client experience; use an API gateway when you need shared infrastructure concerns across many services and clients.

Simple rule of thumb

• API Gateway: “How do all clients securely and consistently reach my APIs?”
• BFF: “How do I make this specific app/device/UI fast, simple, and tailored?”

Use an API gateway when you need:

• Centralized routing to many services
• Authentication/authorization at the edge
• Rate limiting, throttling, quotas
• TLS termination, logging, monitoring
• Request/response forwarding with minimal transformation
• A mostly uniform API contract for many consumers

Good fit: one set of APIs consumed by web, mobile, partners, and internal tools without major differences in data shaping.

Use a BFF when you need:

• Client-specific aggregation and shaping of data
• Different clients need different payloads or workflows
• To reduce overfetching/underfetching for a given UI
• To hide backend complexity from a specific frontend team
• To support frontend-driven evolution without forcing backend changes for every UI need
• To work around mobile latency/bandwidth constraints or specific screen flows

Good fit: one BFF for web, another for mobile, each tailored to the needs of that frontend.

Common examples

BFF is better

• A mobile app needs a compact response with only fields needed for a screen
• A web dashboard needs data combined from orders, payments, and user profile in one call
• Different frontends need different authentication/session handling
• You want frontend teams to own their own API layer

API gateway is better

• You need a single entry point for dozens of microservices
• You want consistent security and observability across all APIs
• You mainly need proxying, policy enforcement, and traffic management

Important distinction

They’re not mutually exclusive:

• An API gateway can sit in front of everything
• One or more BFFs can sit behind the gateway and serve specific clients

A common pattern is:

Client → API Gateway → BFF → Microservices

Decision shortcut

Choose BFF if the main problem is:

• UI-specific composition
• Different client needs
• Frontend performance and ergonomics

Choose API gateway if the main problem is:

• Platform-wide control
• Security
• Routing
• Operational consistency

If you want, I can also give you a decision matrix or a microservices architecture diagram showing where each fits.