From Elastic Beanstalk to AWS Lambda: Going Serverless with Java APIs ??

Earlier this week, I shared how to deploy a Java Spring API on AWS Elastic Beanstalk (?? Deploying a Java Spring Boot API on AWS Elastic Beanstalk). Today, let’s take the same API and reimagine it as a serverless function using AWS Lambda!

Why Lambda?

• Zero server management: No EC2 instances to provision or scale.
• Pay-per-use billing: Cost-effective for sporadic traffic.
• Event-driven: Perfect for APIs, cron jobs, or integrations with S3, DynamoDB, etc.

Step 1: Refactor Your Spring API for Lambda

Lambda works best with lightweight functions. Instead of a full Spring app, we’ll simplify:

1. Add the AWS Lambda Java Core dependency (Maven):

<dependency>  
    <groupId>com.amazonaws</groupId>  
    <artifactId>aws-lambda-java-core</artifactId>  
    <version>1.2.2</version>  
</dependency>         

1. Create a Lambda handler for your API logic:

Step 2: Build and Package

Package your code as a JAR (include all dependencies):

mvn clean package shade:shade          

Step 3: Deploy to AWS Lambda

Option 1: AWS Management Console

1. Go to Lambda > Create Function.
2. Upload your JAR.
3. Set the handler class: com.example.ApiHandler::handleRequest.

Option 2: AWS SAM CLI (Infrastructure-as-Code):

1. Create a template.yaml:

1. Deploy:

Step 4: Connect to API Gateway

Lambda needs a trigger. Create an API Gateway HTTP API:

1. In the Lambda console, click Add Trigger.
2. Choose API Gateway and configure routes (e.g., GET /hello).
3. Deploy the API and test the endpoint!

Key Considerations

• Cold Starts: Lambda may have latency on first invocation. Mitigate with:
• Provisioned concurrency (for critical APIs).
• Keep functions lightweight.
• Statelessness: Lambda functions are ephemeral, so avoid an in-memory state.
• Dependencies: Keep your JAR lean to reduce deployment time.

Elastic Beanstalk vs. Lambda: When to Use Which?

• Elastic Beanstalk:
• Long-running apps with steady traffic.
• Full control over environment (e.g., Spring MVC, databases).
• Lambda:
• Sporadic traffic or event-driven workflows.
• Microservices or single-purpose APIs.
• Cost optimization for low-to-moderate usage.

Final Thoughts

Serverless isn’t a silver bullet, but AWS Lambda is a game-changer for Java developers embracing event-driven architectures. It’s faster to deploy, cheaper at scale, and scales infinitely without DevOps overhead.

Your Turn! Have you used Lambda for Java APIs? What challenges did you face? Let’s chat in the comments! ??

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