Tutorials Microservices with .NET

JWT Authentication in API Gateway — Complete Guide

JWT Authentication in API Gateway — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of Microservices with .NET on Toolliyo Academy.

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Microservices with .NET · Lesson 50 of 120

API Gateway Security

Beginner ✓IntermediateAdvancedProfessional

Intermediate · 2 — Building services · ~6 min · Module 5: API Gateway

What is this?

API Gateway Security is a key part of ShopNest Cloud-Native — your .NET microservices learning project. In plain terms: it helps User Service work correctly in a distributed system where each app deploys and scales on its own.

Why should you care?

You care about this when mobile apps and browsers need one front door URL — not eight different service ports.

See it live — copy this example

Create a Web API project (dotnet new webapi), paste the code, then run dotnet run.

builder.Services.AddReverseProxy()
    .LoadFromConfig(builder.Configuration.GetSection("ReverseProxy"));

// appsettings: /api/orders → order-cluster

Run Example »

This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.

What happened?

  • The example shows API Gateway Security wired into User Service.
  • Read each line, run it locally, then change one setting and observe what breaks or improves.
  • That is how teams learn in production too — small experiments, not big bang rewrites.

Try it yourself

  1. Open or create the ShopNest project area for User Service.
  2. Apply the API Gateway Security pattern from the lesson example.
  3. Run dotnet build && dotnet run (or docker compose up when the lesson uses containers).
  4. Change a string or number in the example and run again — predict the output first.
  5. Break the code on purpose (remove a semicolon), read the compiler error, then fix it.

Remember

API Gateway Security connects to User Service in ShopNest Cloud-Native. Practice by editing the example yourself — do not only read. Move on when you can explain this topic in your own words without looking.

Real-world: HDFC-style fund transfer

Transfer, ledger, fraud check, and SMS run as separate services with idempotency keys. Saga compensates if fraud blocks after debit.

Outcome: Salary-day load handled without duplicate debits or shared-database locks.

Interview prep for this lesson

Practice these questions aloud after reading—each links to a full structured answer.

Mid PDF Detailed
Allow Origins: Configure each microservice’s API Gateway or backend to allow?
Short answer: cross-origin requests from trusted domains. Real-world example (ShopNest) ShopNest’s API Gateway routes /orders to the Order service and /payments to Payment—clients talk to one entry point. Say this in the…
Mid PDF Detailed
API Gateway Security: Use the API Gateway to manage security, including?
Short answer: uthentication, rate-limiting, and access control. Real-world example (ShopNest) ShopNest’s API Gateway routes /orders to the Order service and /payments to Payment—clients talk to one entry point. Say this…
Mid PDF Detailed
Centralized Authentication: Use a central authentication service (e.g., Auth0,?
Short answer: Keycloak) to handle user login and issue access tokens (JWT). The authentication service verifies credentials (e.g., username/password) and provides tokens for users to access microservices. Say this in the…
Mid PDF Detailed
API Gateway: Use the API Gateway to enforce rate limits based on client IP or API?
Short answer: API Gateway: Use the API Gateway to enforce rate limits based on client IP or API? is a common interview topic in Microservices. Give a clear definition, then one concrete example. Real-world example (ShopN…
Senior PDF Detailed
Distributed Transactions: Using Two-Phase Commit (2PC) or Sagas to ensure?
Short answer: that a transaction either commits or rolls back across multiple services. Real-world example (ShopNest) After payment succeeds, ShopNest publishes OrderPaid . Inventory and Notification services react indep…
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Microservices with .NET
Course syllabus

Microservices with .NET Tutorial

Module 1: Foundations and Fundamentals
Module 2: Building User Microservice
Module 3: ShopNest Services and Integration
Module 4: RabbitMQ and Messaging
Module 5: Saga and Distributed Transactions
Module 6: API Gateway
Module 7: gRPC, CQRS, and GraphQL
Module 8: Resiliency and Fault Tolerance
Module 9: DevOps and Cloud-Native
Module 10: Git and GitHub
Module 11: CI/CD Pipelines
Module 12: Observability and Testing
Module 13: Advanced Topics
Module 14: Real-World Enterprise Projects
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