System Type: Web Service

Patterns, failure modes, and anti-patterns for request/response web services.

API Patterns

REST

When to use. Public APIs, browser-facing services, CRUD-heavy domains, when discoverability and cacheability matter. When to avoid. Highly relational data with many nested queries (N+1 fetches). Real-time bidirectional communication. High-throughput internal service-to-service calls where payload efficiency matters. Key decisions. Resource naming, versioning strategy (URL vs header), pagination approach, error format.

GraphQL

When to use. Multiple client types needing different data shapes from the same backend. Complex, nested data relationships. When frontend teams need to iterate independently from backend. When to avoid. Simple CRUD APIs. Server-to-server communication. When caching at the HTTP layer is important (GraphQL's POST-based model breaks HTTP caching). When the team doesn't have GraphQL operational expertise. Key decisions. Schema-first vs code-first, query complexity limits, N+1 resolution strategy (DataLoader pattern), authorization model.