Modern API Integration Patterns & Best Practices

"REST vs GraphQL" is usually the wrong debate — most systems we build end up using both, plus an event-driven layer for anything that isn't a direct request/response. The real skill is matching the pattern to the actual access pattern, not picking a favourite up front.

REST for the boring, stable surface

REST remains the right default for public and partner-facing APIs: cacheable, well-understood, easy to document, and forgiving of client diversity. If the contract needs to stay stable for third parties you don't control, REST's rigidity is a feature.

GraphQL where clients need flexibility

GraphQL earns its complexity when you have multiple frontends (web, mobile, partner dashboards) with genuinely different data needs from the same backend. The upfront cost — schema design, resolver performance, query complexity limits — only pays off once over-fetching or under-fetching becomes a real product problem.

Event-driven for anything asynchronous

• Order placed → inventory, billing and notification services react independently
• Webhooks out to third parties, with signed payloads and retry/backoff
• Internal event bus (SQS/SNS, Kafka, or Pub/Sub) to decouple services that don't need to know about each other
• Idempotency keys everywhere an event might be delivered more than once — because it will be

The pattern that ages badly

The integration architecture we regret most, in hindsight, is always the one picked for resume-driven reasons rather than the actual shape of the traffic. Start from how your clients actually need to read and write data, and let the pattern follow.