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API Gateway with Spring Boot

Learn how to integrate Amazon API Gateway with Spring Boot step by step. This guide covers API Gateway architecture, REST APIs, HTTP APIs, authentication, throttling, caching, custom domains, monitoring, and production best practices.

Introduction

Modern applications rarely expose backend services directly to clients.

Instead of clients calling a Spring Boot application running on EC2, ECS, or EKS, requests first pass through an API Gateway.

An API Gateway acts as the single entry point for all client requests.

It provides:

  • Authentication
  • Authorization
  • Rate Limiting
  • Request Routing
  • API Versioning
  • Monitoring
  • Logging
  • Security

Amazon API Gateway is AWS's fully managed service for creating, publishing, securing, monitoring, and managing APIs.

In this article, we will integrate Spring Boot applications with Amazon API Gateway and understand enterprise API architectures.

Learning Objectives

After completing this article, you will understand:

  • What is API Gateway?
  • Why API Gateway is required
  • REST API vs HTTP API
  • API Gateway Architecture
  • Spring Boot Integration
  • Request Flow
  • Authentication
  • Authorization
  • API Keys
  • Usage Plans
  • Throttling
  • Caching
  • Monitoring
  • Production Best Practices

Why API Gateway?

Without API Gateway:

Client

↓

Spring Boot

Problems:

  • No centralized security
  • No rate limiting
  • Difficult monitoring
  • No API versioning
  • Direct backend exposure

With API Gateway

Client

↓

API Gateway

↓

Spring Boot

Benefits:

  • Centralized security
  • Authentication
  • Logging
  • API management
  • Better scalability

High-Level Architecture

flowchart LR
    Client

    APIGateway

    SpringBoot

    Aurora

    Client --> APIGateway
    APIGateway --> SpringBoot
    SpringBoot --> Aurora

Enterprise Architecture

flowchart TD

Users

CloudFront

AWSWAF

API_Gateway

ALB

SpringBoot

Redis

Aurora

CloudWatch

Users --> CloudFront
CloudFront --> AWSWAF
AWSWAF --> API_Gateway
API_Gateway --> ALB
ALB --> SpringBoot
SpringBoot --> Redis
SpringBoot --> Aurora
SpringBoot --> CloudWatch

What is API Gateway?

API Gateway is a managed service that sits between clients and backend services.

Responsibilities:

  • Route requests
  • Authenticate users
  • Validate requests
  • Throttle traffic
  • Cache responses
  • Transform requests
  • Monitor APIs

API Gateway Types

AWS supports:

Type Best For
REST API Enterprise APIs
HTTP API Lightweight APIs
WebSocket API Real-time communication

For Spring Boot microservices:

REST API and HTTP API are commonly used.

REST API vs HTTP API

Feature REST API HTTP API
Cost Higher Lower
Performance Good Faster
API Keys Yes Limited
Usage Plans Yes No
Caching Yes No
Enterprise Features More Fewer

Real-Time Use Cases

API Gateway is commonly used for:

  • Mobile Applications
  • Banking APIs
  • E-Commerce APIs
  • Insurance Platforms
  • SaaS Applications
  • Internal APIs
  • Partner APIs

Request Flow

flowchart LR

Browser

API_Gateway

SpringBoot

Database

Browser --> API_Gateway
API_Gateway --> SpringBoot
SpringBoot --> Database

API Gateway Features

Supports:

  • Authentication
  • Authorization
  • SSL
  • Request Validation
  • Rate Limiting
  • API Keys
  • Usage Plans
  • CORS
  • Monitoring
  • Logging

Step 1 Deploy Spring Boot

Deploy application on:

  • EC2
  • ECS
  • EKS
  • Elastic Beanstalk
  • App Runner

Verify API:

http://your-alb.amazonaws.com/api/employees

Step 2 Create API Gateway

AWS Console

↓

API Gateway

↓

Create API

Choose

HTTP API

or

REST API

Step 3 Configure Backend

Backend Type

HTTP Endpoint

Backend URL

http://your-alb.amazonaws.com

Step 4 Create Routes

Examples

GET /employees

POST /employees

PUT /employees/{id}

DELETE /employees/{id}

Route Mapping

flowchart LR

GET

POST

PUT

DELETE

API_Gateway

SpringBoot

GET --> API_Gateway
POST --> API_Gateway
PUT --> API_Gateway
DELETE --> API_Gateway

API_Gateway --> SpringBoot

Step 5 Deploy API

Create Stage

dev

or

prod

Example URL

https://abc123.execute-api.us-east-1.amazonaws.com/prod

Spring Boot API

Example

GET

/api/employees

Response

[
 {
   "id":1,
   "name":"Venu"
 }
]

Authentication

API Gateway supports:

  • IAM
  • Cognito
  • JWT
  • Lambda Authorizer
  • Custom Authorizer

JWT Flow

flowchart LR

User

JWT

API_Gateway

SpringBoot

User --> JWT
JWT --> API_Gateway
API_Gateway --> SpringBoot

API Keys

API Keys identify applications consuming your APIs.

Example

x-api-key

abc123xyz

Useful for:

  • Partner APIs
  • Internal APIs

Usage Plans

Limit API usage.

Example

1000 Requests

Per Day

or

100 Requests

Per Minute

Throttling

Protect backend services.

Example

Burst

100

Rate

1000/sec

Requests beyond limits receive:

HTTP 429

Too Many Requests

Request Validation

Validate:

  • Headers
  • Path Parameters
  • Query Parameters
  • Request Body

Reject invalid requests before reaching Spring Boot.

CORS

Enable CORS for browser applications.

Allowed:

https://codewithvenu.com

Avoid

*

in production.

API Versioning

Example

/v1/employees

/v2/employees

Allows backward compatibility.

Response Caching

REST APIs support response caching.

Benefits:

  • Faster response
  • Reduced backend load
  • Lower cost

Custom Domain

Instead of

https://abc123.execute-api.amazonaws.com

Use

https://api.codewithvenu.com

Integrate:

  • Route53
  • ACM
  • API Gateway

Monitoring

CloudWatch Metrics

Monitor:

  • Request Count
  • Latency
  • 4XX Errors
  • 5XX Errors
  • Integration Latency
  • Cache Hits

Logging

Enable:

  • Access Logs
  • Execution Logs
  • CloudWatch Logs

Useful for troubleshooting.

Error Handling

Common responses:

Status Meaning
200 Success
400 Bad Request
401 Unauthorized
403 Forbidden
404 Not Found
429 Too Many Requests
500 Internal Server Error

Security

Protect APIs using:

  • HTTPS
  • JWT
  • Cognito
  • AWS WAF
  • IAM
  • API Keys
  • Usage Plans

Never expose sensitive APIs without authentication.

Production Architecture

flowchart TD

Users

Route53

CloudFront

AWSWAF

API_Gateway

ALB

SpringBootAZ1

SpringBootAZ2

Redis

Aurora

CloudWatch

Users --> Route53
Route53 --> CloudFront
CloudFront --> AWSWAF
AWSWAF --> API_Gateway
API_Gateway --> ALB
ALB --> SpringBootAZ1
ALB --> SpringBootAZ2
SpringBootAZ1 --> Redis
SpringBootAZ2 --> Redis
SpringBootAZ1 --> Aurora
SpringBootAZ2 --> Aurora
SpringBootAZ1 --> CloudWatch
SpringBootAZ2 --> CloudWatch

Common Issues

403 Forbidden

Check:

  • Authorization
  • IAM
  • JWT

404 Not Found

Verify:

  • Route
  • Stage
  • Backend URL

502 Bad Gateway

Check:

  • Spring Boot running
  • ALB Target Group
  • Backend integration

CORS Error

Configure:

  • Allowed Origins
  • Allowed Methods
  • Allowed Headers

High Latency

Review:

  • Backend performance
  • Cache configuration
  • Database queries

Best Practices

  • Use HTTP API for lightweight services
  • Use REST API for enterprise features
  • Enable HTTPS
  • Validate requests
  • Use JWT authentication
  • Protect APIs with AWS WAF
  • Configure throttling
  • Enable CloudWatch logging
  • Use custom domains
  • Version APIs
  • Cache frequently accessed responses
  • Monitor error rates
  • Keep backend services private behind ALB

Developer Checklist

Before production deployment:

  • API Gateway created
  • Backend integration configured
  • Routes created
  • Authentication enabled
  • JWT validated
  • CORS configured
  • CloudWatch logging enabled
  • Custom domain configured
  • ACM certificate attached
  • Route53 DNS updated
  • WAF enabled
  • Throttling configured

Interview Questions

What is Amazon API Gateway?

Amazon API Gateway is a fully managed service for creating, securing, monitoring, and managing APIs.

Why use API Gateway with Spring Boot?

It provides a secure entry point, request routing, authentication, throttling, monitoring, and centralized API management.

Difference between REST API and HTTP API?

REST APIs provide advanced enterprise features such as API keys, usage plans, request validation, and caching. HTTP APIs are simpler, faster, and more cost-effective.

What is throttling?

Throttling limits the number of requests accepted by the API to protect backend services from overload.

Why use API Keys?

API Keys identify and manage API consumers, especially for partner and internal APIs.

Can API Gateway integrate with Spring Boot running on ALB?

Yes. API Gateway can route HTTP requests to an Application Load Balancer that fronts Spring Boot applications running on EC2, ECS, or EKS.

Summary

In this article, we learned how to integrate Amazon API Gateway with Spring Boot applications.

We covered:

  • API Gateway fundamentals
  • REST API vs HTTP API
  • Backend integration
  • Routing
  • Authentication
  • JWT
  • API Keys
  • Usage Plans
  • Throttling
  • CORS
  • Monitoring
  • Custom domains
  • Production best practices

Amazon API Gateway is a key component in modern AWS architectures, providing secure, scalable, and manageable API access for Spring Boot microservices while reducing operational complexity.

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