Serverless Spring Boot using AWS Lambda

Running Spring Boot on AWS Lambda lets you combine the power of Java microservices with the scalability and cost-efficiency of serverless computing. With features like Amazon API Gateway, Lambda SnapStart, and native Java support, Spring Boot is now more viable than ever in serverless architectures.

In this guide, you’ll learn:

How to package Spring Boot as a serverless function
How to deploy it on AWS Lambda
Integrate with API Gateway for HTTP access
Improve cold starts using SnapStart
Best practices and limitations

We’ll use the base package:
com.kscodes.springboot.containers

🧰 Prerequisites

You’ll need:

AWS account
AWS CLI installed and configured
Java 17 or 21
Maven or Gradle
Docker (optional for local testing)

🏗️ Step 1: Create a Spring Boot App with AWS Lambda Adapter

Use AWS Serverless Java Container to adapt Spring Boot for Lambda.

`pom.xml` Dependencies:

<groupId>com.amazonaws.serverless</groupId>

<artifactId>aws-serverless-java-container-springboot3</artifactId>

</dependency>

Sample Controller:

package com.kscodes.springboot.containers;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.RestController;

@RestController

public class LambdaHelloController {

@GetMapping("/")

public String index() {

return "Hello from AWS Lambda!";

}

📦 Step 2: Create Lambda Handler

package com.kscodes.springboot.containers;

import com.amazonaws.serverless.exceptions.ContainerInitializationException;

import com.amazonaws.serverless.proxy.model.AwsProxyRequest;

import com.amazonaws.serverless.proxy.model.AwsProxyResponse;

import com.amazonaws.serverless.proxy.spring.SpringBootProxyHandlerBuilder;

import com.amazonaws.services.lambda.runtime.Context;

import com.amazonaws.services.lambda.runtime.RequestHandler;

public class LambdaHandler implements RequestHandler<AwsProxyRequest, AwsProxyResponse> {

private static final SpringBootProxyHandlerBuilder<AwsProxyRequest> handlerBuilder =

new SpringBootProxyHandlerBuilder<AwsProxyRequest>()

.defaultProxy();

private static final var handler = handlerBuilder

.asyncInit()

.springBootApplication(ServerlessApplication.class)

.buildAndInitialize();

@Override

public AwsProxyResponse handleRequest(AwsProxyRequest input, Context context) {

return handler.proxy(input, context);

}

🧪 Step 3: Package for Lambda

Use Spring Boot thin JAR or maven-shade-plugin to build a single Lambda-compatible JAR.

Build Command:

./mvnw clean package

You’ll get a target/serverless-demo.jar.

☁️ Step 4: Create Lambda Function via AWS CLI

aws lambda create-function \

--function-name springboot-lambda \

--runtime java21 \

--handler com.kscodes.springboot.containers.LambdaHandler \

--memory-size 512 \

--timeout 15 \

--zip-file fileb://target/serverless-demo.jar \

--role arn:aws:iam::123456789012:role/lambda-exec-role

Or deploy from S3:

aws s3 cp target/serverless-demo.jar s3://your-bucket/

aws lambda create-function \

--code S3Bucket=your-bucket,S3Key=serverless-demo.jar \

...

🌐 Step 5: Expose with API Gateway

aws apigatewayv2 create-api \

--name springboot-api \

--protocol-type HTTP

Create integration and route the Lambda handler to a URL endpoint.

Use AWS Console or sam/terraform for more flexibility.

🚀 Optional: Enable SnapStart

To reduce cold starts for Java functions:

Deploy function with Java 21.
Enable SnapStart in AWS Console under Function → Configuration → SnapStart.
Redeploy the published version.

SnapStart drastically reduces startup time for Spring Boot functions.

📈 Monitoring and Logs

View logs in CloudWatch:

aws logs tail /aws/lambda/springboot-lambda --follow

Monitor latency, cold starts, invocations, and errors in AWS Lambda metrics.

🛡️ Best Practices

Tip	Description
Use SnapStart	Reduces Spring Boot cold starts to milliseconds
Keep JAR minimal	Remove unused dependencies, enable lazy init
Limit memory/cpu usage	Helps reduce cost per invocation
Use Lambda Powertools (Java)	Logging, tracing, metrics libraries from AWS
Use CI/CD with SAM or Terraform	Automate packaging and deployment

⚖️ When to Use Serverless for Spring Boot?

✅ Good for:

Event-driven microservices
Low-traffic APIs
Scheduled jobs (via EventBridge)
Rapid POC deployment

🚫 Not ideal for:

Long-running processes
Applications needing consistent low latency
Apps with heavy startup loads (without SnapStart)

🧠 Summary

You just learned how to deploy a Spring Boot application as a serverless AWS Lambda function, configure API Gateway, reduce cold starts with SnapStart, and automate everything with AWS CLI.

This model provides a cost-effective, scalable, and devops-free solution for Spring Boot apps, especially for bursty workloads.