How API Gateway Works

Source: Dev.to

What is an API Gateway?

An API Gateway is a single entry point that receives all client requests and routes them to the appropriate backend services while handling security, traffic control, and monitoring.

In modern microservices architecture, clients never communicate directly with backend services. Instead, all requests pass through the API Gateway, improving security, scalability, and system control.

How to code an API Gateway (Cloud Native) using Cloudflare
https://youtu.be/D4Lt18qYkjc

How API Gateway Works

An API Gateway sits between the client and backend services and processes every request in the following steps:

1. Receives the incoming request from the client (web, mobile, or frontend)
2. Authenticates and validates the request
3. Applies rate limiting and throttling
4. Routes the request to the correct backend service
5. Collects logs, metrics, and traces
6. Sends the response back to the client

This entire process happens within milliseconds.

API Gateway Request Flow

Client
   ↓
API Gateway
   ↓
Authentication
   ↓
Rate Limiting
   ↓
Routing
   ↓
Backend Services
   ↓
Response

Why API Gateway Is Important

Problems without an API Gateway

• Complex frontend logic
• Security exposed at multiple points
• Difficult authentication handling
• No centralized monitoring
• Hard to scale independently

Benefits with an API Gateway

• Single secure entry point
• Centralized authentication
• Traffic control and rate limiting
• Better observability
• Easier microservice scaling

Core Responsibilities of an API Gateway

1. Authentication & Authorization

The gateway verifies tokens (JWT, OAuth, API keys) before forwarding requests.

2. Routing

Requests are routed to the correct services based on path, method, or headers.

Example

• /users → User Service
• /orders → Order Service

3. Rate Limiting

Prevents abuse by limiting how many requests a client can make per second.

4. Load Balancing

Distributes traffic across multiple backend instances.

5. Observability

Collects logs, metrics, and distributed traces—critical for production systems.

API Gateway in Microservices Architecture

In microservices, each service is deployed independently. The API Gateway acts as:

• A boundary
• A security layer
• A traffic controller

It protects backend services from direct exposure to the internet.

Common API Gateway Examples

• Cloudflare Workers (edge‑based)
• Kong
• NGINX
• AWS API Gateway
• Apigee
• Traefik

Each tool differs in performance, cost, and architecture.

Edge API Gateway vs Traditional Gateway

Traditional API Gateway

• Runs on centralized servers
• Higher latency
• Regional deployments

Edge API Gateway

• Runs close to users
• Ultra‑low latency
• Global availability

Cloudflare Workers is a strong example of an edge‑based API Gateway.

When Should You Use an API Gateway?

Use an API Gateway when you:

• Have multiple backend services
• Need centralized security
• Want traffic control
• Require observability
• Are building scalable systems

For simple monolithic apps, an API Gateway may not be necessary.

Real‑World Example

A frontend application sends a request:

GET /api/orders

The API Gateway:

1. Validates the user token
2. Checks the rate limit
3. Routes the request to the Order Service
4. Logs request metrics
5. Returns the response

The frontend never interacts directly with backend services.

Practical Implementation

A complete hands‑on tutorial is available on the CodingMavrick YouTube channel. The video covers:

• Building an API Gateway using Cloudflare Workers
• Routing logic
• Authentication
• Rate limiting
• Observability integration
• Production deployment