API and Communication

Welcome to Module 03. In the previous modules, we covered the basics of Networking and the Mindset of a System Architect. Now, we dive into the Language of Systems. How do services talk to each other? How do clients talk to servers?

🎯 Learning Objectives

By the end of this module, you will be able to:

  1. Design robust REST APIs using standard methods, status codes, and standard error formats like Problem+JSON (RFC 7807).
  2. Evaluate GraphQL and understand when to use it over REST, including advanced Directive-based Auth and CDN Caching via Persisted Queries.
  3. Implement Real-Time features using WebSockets, SSE, and peer-to-peer WebRTC Data Channels.
  4. Architect an API Gateway at the Edge to handle rate limiting, auth, SSL termination, and global routing.

📚 Chapter List

Chapter Topic Key Concepts
01 REST API Design Strategies CRUD, Problem+JSON, E-Tags, Idempotency, gRPC.
02 GraphQL Basics Schema Directives, Persisted Queries, N+1 Problem, Federation.
03 Polling vs Push WebSockets, SSE, WebRTC Data Channels, HTTP/3.
04 API Gateway Pattern Edge Computing, Rate Limiting, BFF, Service Mesh, RED Method.

🛠️ Prerequisite Knowledge

  • Basic HTTP (Headers, Body, Verbs).
  • Understanding of “Client-Server” architecture.
  • (Optional) Experience with Express.js or Spring Boot.

🚀 Interactive Labs

Each chapter in this module contains an Interactive Decision Visualizer.

  • REST Terminal: Send requests and see how the server responds.
  • N+1 Visualizer: Watch how GraphQL can kill your database.
  • Protocol Racer: Compare the latency of Polling vs WebSockets.
  • Gateway Policy Simulator: Act as a “Bouncer” for your backend.

Let’s begin with the lingua franca of the web: REST API Design.

Module Chapters