🌐 API Gateway: The Front Door to Microservices

🌐 API Gateway: The Front Door to Microservices

How to implement API Gateway in Spring Cloud — with one unified access point, routing, security, and monitoring.

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1️⃣ 🔗 Unified Entry Point

🎯 Goal:
One access door for all services 🏠

🛠️ Tech Stack:
Spring Cloud Gateway, Netflix Zuul, Kong

🌐 Real-Time Use Case:
A mobile app makes a call to one endpoint; the gateway routes to 10+ microservices behind the scenes.

❌ Problem Solved:
No exposure of internal microservice URLs or architecture to the client.

🧑‍💻 Implementation Steps:
1. Add spring-cloud-starter-gateway to your pom.xml
2. Define routes in application.yml using spring.cloud.gateway.routes
3. Integrate with Eureka for dynamic discovery (optional)
4. Run and test routing with tools like Postman or curl

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2️⃣ 🚦 Smart Routing & Load Balancing

🎯 Goal:
Dynamic traffic control between microservices

🛠️ Tech Stack:
Spring Cloud LoadBalancer, Eureka, Ribbon (legacy)

🌐 Real-Time Use Case:
Gateway receives /orders → routes to OrderService; /auth → routes to AuthService.

❌ Problem Solved:
Clients don’t need to know microservice IPs or internal service structure.

🧑‍💻 Implementation Steps:
1. Register all services with Eureka
2. Enable load balancing via Spring Cloud Gateway or Spring Cloud LoadBalancer
3. Set up service name routing (e.g., lb://orders-service)
4. Gateway will round-robin requests across available service instances

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3️⃣ 🛡️ Centralized Security

🎯 Goal:
Validate tokens and apply security logic at one place.

🛠️ Tech Stack:
Spring Security, OAuth2 Resource Server, JWT, Keycloak

🌐 Real-Time Use Case:
Gateway verifies JWT tokens before allowing access to any downstream service.

❌ Problem Solved:
Avoids duplicating security logic in every microservice; one gateway handles it all.

🧑‍💻 Implementation Steps:
1. Configure Spring Security on the Gateway project
2. Use spring-security-oauth2-resource-server to decode and validate JWT
3. Add security filters to allow/deny requests
4. Integrate with OAuth2 provider (e.g., Keycloak)

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4️⃣ 🚫 Rate Limiting & Throttling

🎯 Goal:
Throttle high-frequency calls to prevent abuse

🛠️ Tech Stack:
Bucket4j, Redis, Resilience4j

🌐 Real-Time Use Case:
Free-tier users limited to 1000 API calls/day; gateway blocks excess calls.

❌ Problem Solved:
Protects services from spikes or DoS-like usage and maintains API availability.

🧑‍💻 Implementation Steps:
1. Add Bucket4j or Redis-based rate limiter to the Gateway
2. Define rules (per IP/user) in configuration
3. Integrate rate limiter via filters or Gateway predicates
4. Return HTTP 429 (Too Many Requests) when limits are exceeded

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5️⃣ 📈 Logging, Monitoring & Transformation

🎯 Goal:
Trace requests, log structured data, transform payloads if needed

🛠️ Tech Stack:
Spring Cloud Sleuth, Zipkin, ELK Stack, Spring Boot Actuator

🌐 Real-Time Use Case:
Gateway adds request ID in logs, transforms headers for backward compatibility.

❌ Problem Solved:
Eases debugging, audit trails, and traffic inspection.


🧑‍💻 Implementation Steps:
1. Add spring-cloud-starter-sleuth for distributed tracing
2. Send trace data to Zipkin or ELK Stack
3. Create custom filters to modify headers or request body
4. Expose actuator endpoints for metrics and health checks

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🔁 API Gateway Summary:

One Gateway =
Security 🔐 + Routing 🚦 + Rate Limiting 🚫 + Logging 🔍 + Transformation 🎭

It simplifies microservice management, secures traffic, and improves reliability.

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📋 Want the Full Code & Implementation Details?

👉 Download Here (Google Drive)