API Design & Integration Patterns
Building an API that works is table stakes. Building an API that's correct, consistent, backwards compatible, secure, and a pleasure to use for the developers integrating with it — that's the skill that matters in professional settings. The difference shows up when your first client tries to integrate, when you need to change a field name without breaking existing consumers, or when someone's integration fails and the only clue is a 500 with no body. This module teaches API design as a discipline. You'll understand the REST constraints — not as rules to follow but as consequences of the underlying architectural style — and apply them to make APIs that are predictable and self-documenting. You'll understand versioning strategies and their tradeoffs, implement cursor-based pagination that handles concurrent writes correctly, and design authentication patterns using API keys, OAuth 2.0 flows, and JWTs with proper claims design. You'll also get practical experience with GraphQL — schema-first design, solving the N+1 problem with DataLoader, and subscriptions for real-time data. And you'll produce proper API documentation using OpenAPI specifications, because an undocumented API is a support burden waiting to happen. The capstone project requires implementing all of these patterns in a single API, demonstrating that you can design and build a production-quality interface.
What You'll Learn
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1
REST API Design Principles — Resource naming, HTTP semantics, Richardson Maturity Model
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2
API Versioning Strategies — URL, header, query param versioning, sunset headers
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3
Pagination — Offset vs cursor vs keyset, handling concurrent writes
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4
Authentication Patterns — API keys, OAuth 2.0 flows, JWT design, mutual TLS
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5
Rate Limiting and Throttling — Token bucket, sliding window, rate limit headers
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6
GraphQL Design — Schema-first, N+1 problem, DataLoader, subscriptions
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7
API Documentation — OpenAPI/Swagger, code generation, spec-first development
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8
Idempotency, Backwards Compatibility, and Error Design — Error standards, SDK design
Capstone Project: Design and Implement a Complete API with Versioning, Pagination, Rate Limiting, Webhooks, and Auto-Generated Documentation
Design and implement a complete REST API for a multi-tenant SaaS product — with URL versioning, cursor-based pagination, OAuth 2.0 authentication, per-tenant rate limiting, webhook delivery with HMAC verification and retry logic, and a fully generated OpenAPI specification. The API must handle backwards-compatible changes between v1 and v2, include comprehensive error responses following RFC 7807 (Problem Details), and have 100% API test coverage.
Why This Matters for Your Career
APIs are the long-lived interfaces of your system. Unlike internal code that can be refactored freely, an API that has external consumers cannot be changed without coordination and potential breakage. Engineers who design APIs well — with clear resource models, correct HTTP semantics, proper versioning, and graceful deprecation — save their teams enormous amounts of backwards-compatibility work and consumer support. Authentication design in particular has serious security implications. Improperly signed JWTs, overly broad OAuth scopes, API keys stored in git history, missing rate limiting on authentication endpoints — these are the kinds of issues that lead to security incidents. Engineers who understand authentication patterns deeply implement them correctly the first time. GraphQL adoption continues to grow for APIs with complex, interconnected data models and diverse clients. Understanding the N+1 problem — and its DataLoader solution — is essential for anyone building GraphQL APIs at scale. The engineers who understand both REST and GraphQL as architectural styles, rather than just knowing how to call them, can make informed decisions about which to use for a given problem.