Serverless on Java: AWS Lambda and Alternatives for Backend

Serverless on Java: Why It's Not Scary and Even Profitable?

When you hear "serverless," the first association is Node.js or Python. Java seems like a heavyweight that "starts slowly" and "eats a lot of memory." But let's face the truth: Java remains the corporate standard, and modern serverless is not just "run a function and forget it." It's an architecture that can save you a ton of money and nerves if you approach it wisely.

In this article, we'll break down how to write serverless functions in Java, using AWS Lambda as an example, and also consider alternatives: Google Cloud Functions, Azure Functions, and the Vercel platform. You'll learn what pitfalls await a Java developer in the serverless world and how to avoid them. Let's go!

What is serverless and why Java?

Serverless (or FaaS — Function as a Service) is a cloud computing model where you write code, upload it to the cloud, and the provider decides when and how to run it. You pay only for the actual execution time and number of requests. No servers, no infrastructure management.

Why Java? There are several reasons:

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• Stability and maturity. Java, with its strict typing and proven libraries, is ideal for enterprise tasks.
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• Performance. Modern JVMs (especially GraalVM) can reduce cold start time to milliseconds.
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• Ecosystem. Spring Boot, Micronaut, Quarkus — all of them are adapted for serverless.
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But there is a nuance: the "cold start" in Java can be longer than in Python or Go. However, with the right tools, this can be solved.

AWS Lambda: The Main Player in the Serverless Java Market

AWS Lambda is perhaps the most popular service for serverless functions. It supports Java "out of the box" and offers two paths: classic Java 8/11/17 and SnapStart (a technology that makes cold starts practically unnoticeable).

Writing Your First Lambda Function in Java

Let's create a simple function that processes HTTP requests via Amazon API Gateway. For this, we'll need a Maven project and a couple of dependencies.

Step 1. Create a Maven project with the following pom.xml:

<?xml version="1.0" encoding="UTF-8"?>\n<project xmlns="http://maven.apache.org/POM/4.0.0"\n         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"\n         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0\n         http://maven.apache.org/xsd/maven-4.0.0.xsd">\n    <modelVersion>4.0.0</modelVersion>\n\n    <groupId>com.pythonlib</groupId>\n    <artifactId>serverless-java</artifactId>\n    <version>1.0-SNAPSHOT</version>\n\n    <dependencies>\n        <dependency>\n            <groupId>com.amazonaws</groupId>\n            <artifactId>aws-lambda-java-core</artifactId>\n            <version>1.2.2</version>\n        </dependency>\n        <dependency>\n            <groupId>com.amazonaws</groupId>\n            <artifactId>aws-lambda-java-events</artifactId>\n            <version>3.11.3</version>\n        </dependency>\n    </dependencies>\n\n    <build>\n        <plugins>\n            <plugin>\n                <groupId>org.apache.maven.plugins</groupId>\n                <artifactId>maven-shade-plugin</artifactId>\n                <version>3.2.4</version>\n                <executions>\n                    <execution>\n                        <phase>package</phase>\n                        <goals><goal>shade</goal></goals>\n                    </execution>\n                </execution