API and Integration Guide

API and integration development is building bridges that let different systems (website, mobile app, ERP, CRM, payment, shipping, e-invoice) talk to each other. Properly designed APIs and robust integrations prevent data duplication, reduce manual work, and increase system reliability. As of 2026, API-first architecture has become the standard of modern software development.

REST vs GraphQL vs tRPC

REST: mature, wide ecosystem, multi-endpoint logic. Ideal for public APIs and broad client compatibility. GraphQL: single endpoint, flexible queries, frontend-friendly — fetches as much data as the client needs. Excels with complex data structures, mobile + web sharing same API. tRPC: TypeScript-first, end-to-end type safety — preferred in Next.js + monorepo ecosystem. gRPC: high performance, for microservice-to-microservice communication. The right choice based on client type, team capability and performance requirements.

Third-party Integration Strategies

Integration patterns: Webhook (push) — opposing system notifies on event, most efficient. Polling (pull) — periodic query, simple but less efficient. Event bus — event-driven architecture with Apache Kafka, Redis Streams, RabbitMQ. Message queue — async workload, retry, dead letter queue. Each integration has different characteristics: payment webhook (high priority), shipping polling (hourly), CRM event bus (real-time). Wrong pattern choice creates major scale issues.

Auth and Security

OAuth 2.0: third-party access on behalf of user (Google login, GitHub OAuth, etc.). JWT: stateless token, short-lived access + long-lived refresh token. API key: server-to-server, simple but rotation needed. mTLS: high-security needed finance/healthcare integrations. Rate limiting: token bucket, sliding window — abuse protection. Request signing: message verification with HMAC, critical in webhooks. Security design determined per integration's risk model.

Error Handling and Resilience

Production-grade integration must be resilient. Retry with exponential backoff: 1s, 2s, 4s, 8s — retry on transient errors. Circuit breaker: open circuit if opposing system continuously errors (Hystrix, Resilience4j patterns). Idempotency key: same request twice = same result (mandatory in payment integrations). Dead letter queue: unprocessable messages — analysis and manual re-process. Monitoring: Sentry, Datadog, error rate alerting. Errors are not surprises, but planned conditions.

Public API Publishing

Public API offered to your customers requires great responsibility. Versioning: v1, v2 (new version when breaking changes). Rate limiting: per-customer plan minute/hour/day limits. OpenAPI spec: standard for documentation and client SDK generation. Swagger UI or Redoc for interactive documentation. Terms of service, deprecation policy (notice at least 6 months in advance), changelog. Status page (Statuspage, Cachet) for uptime transparency. Sandbox environment critical for customer onboarding.