LEVEL 9 · BACKEND ENGINEERING

Course Core

API engineering

Design APIs other people can depend on: REST resources and contracts, pagination and versioning, idempotency and safe retries, rate limiting, and contracts that evolve without breaking clients.

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When you finish, you can

  • Design resources, URLs, status codes and error bodies
  • Paginate with offsets and cursors and version an API
  • Make a payment endpoint idempotent
  • Rate-limit an API fairly
  • Evolve a contract without breaking existing clients

You build: A money-transfer API that is safe to retry and safe under load

MODULE 1

Designing APIs

  1. 1Pagination and versioning in depthPage through 100,000 orders without skipping or repeating one, design opaque cursors, and change responses without breaking existing clients.50 min

MODULE 2

APIs under real traffic

  1. 2Idempotency and safe retriesBuild a ₦10,000 transfer endpoint that survives partial failures, lost responses, double taps and crashes, with transactions and idempotency keys.55 min
  2. 3Rate limitingBuild fixed-window, sliding-window and token-bucket rate limiters, choose what to count, answer 429 with Retry-After, and share limits across servers.50 min
  3. 4API contractsWrite an OpenAPI contract by hand, enforce it with schema validation, catch breaking changes with contract tests, and version events and serialization.55 min

Course checkpoint

Prove you can move on. The checkpoint picks 20 questions at random from every lesson in this course. Get 16 right to pass. Your result is saved in this browser only.