Proxy + Adapter for API Integration

When connecting a frontend to a third-party API, it’s rarely wise to expose that API directly.
Instead, you can insert a Proxy + Adapter layer — a small backend service that sits between the UI and the external system.

This layer doesn’t just pass requests through; it reshapes, secures, and stabilizes the integration.

Core Benefits

1. Security

• API keys stay server-side.
• The UI never needs to know credentials or vendor details.
• Limits the attack surface: you can validate and sanitize inputs centrally.

2. Consistency

• The frontend always gets a normalized response shape.
• Error handling and fallbacks are unified.
• Different external services can be swapped behind the same interface.

3. Flexibility

• You can translate simple UI parameters into whatever complex query structure the vendor requires.
• Can add features like caching, throttling, logging, or enrichment before data hits the client.
• Enables experimentation without rewriting the entire frontend.

Pattern Components

• Proxy: Forwards requests to the external API on behalf of the client.
• Adapter: Translates between your internal parameter model and the vendor’s expected payloads.
• Decorator (optional): Adds extras like caching, deduplication, or resilience patterns.

Together, these make up a Backend-for-Frontend (BFF) approach: an endpoint designed specifically for the needs of a single UI.

When to Use

Use this pattern when:

• The third-party API is complex, verbose, or unstable.
• You want to shield your frontend from vendor lock-in.
• You need normalized, predictable data contracts.
• You expect to change providers, but don’t want to change your UI.
• You want to enforce security, rate limiting, or caching centrally.

Avoid it only when:

• Your frontend is purely internal and latency is more critical than maintainability.
• The external API is already simple, stable, and client-safe.

Example Scenarios

• Wrapping a search API so the UI just posts { q, filters } and always gets { results, count, facets }.
• Exposing payment flows through a /checkout endpoint instead of hitting Stripe/PayPal SDKs directly.
• Creating a unified /profile API that pulls from multiple upstream systems but feels like one to the UI.

Reflections

This pattern feels like over-engineering at first, but it becomes invaluable as soon as:

• The vendor changes their API schema.
• You add a second integration.
• You want to swap implementations without rewriting the app.

Like many architecture choices, it’s a trade-off between simplicity now and stability later — and it’s often worth the thin layer.