Tutorials System Design Tutorial
API Gateway for Microservices — Complete Guide
API Gateway for Microservices — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of System Design Tutorial on Toolliyo Academy.
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System Design Tutorial · Lesson 15 of 100
API Gateway for Microservices
Basics → Scale → Interview
Basics · 1 — Building blocks · ~6 min · Module 2: Networking and Traffic Management
What is this?
An API gateway is the single external entry for many services — auth, rate limits, routing, and request shaping.
Why should you care?
Mobile apps should not know twenty ShopNest internal URLs and auth schemes.
See it live — copy this example
Sketch the architecture on paper. These lessons focus on concepts and trade-offs.
App → API Gateway
├─ /catalog/** → Catalog service
├─ /orders/** → Order service
└─ /pay/** → Payment service
Gateway: JWT validate, rate limit, request IDRun Example »
This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.
What happened?
- The gateway centralizes edge policies.
- Business logic still lives in services.
- Avoid turning the gateway into a giant orchestrator of business workflows.
Practice next
- Map three ShopNest routes to services.
- Put JWT validation at the gateway.
- Add a global rate limit per user id.
- Add an internal admin gateway separate from public.
- Strip external headers that should not reach apps.
Remember
One external front door. Policy at edge; domain logic in services. Route by path or host.
ShopNest public gateway
Mobile uses one base URL; gateway routes and auths.
Outcome: Internal services stay private on the VPC network.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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