I'm exploring the use of GraalVM in my AWS Lambda projects, specifically with a Kotlin and Micronaut application. I'm intrigued about the practical use cases for GraalVM in Lambda setups since I'm facing several challenges, particularly with asynchronous operations like writing to Kinesis—there are hidden dependencies that don't play nicely with GraalVM. Does anyone have solid examples or reasons for using GraalVM in Lambda beyond just the theoretical benefits?
4 Answers
Have you checked out Class Data Sharing (CDS) or the Ahead-of-Time (AOT) compilation features in Java 25? They can really help with improving your startup time. Here are some resources to look into:
- [CDS](https://blog.jdbevan.com/2020/09/30/java-11-appcds-example-with-gradle/)
- [AOT](https://aws.amazon.com/blogs/compute/aws-lambda-now-supports-java-25/)
From my experience a few years back, converting a Java Lambda to GraalVM wasn't straightforward due to lots of specific challenges, especially with larger frameworks like Spring. The highlight of GraalVM is its ahead-of-time compilation, which can reduce cold start times. However, if your code has quirks or dependencies that don't align, it can become a hassle to get it working.
GraalVM is known for its fast startup times, which can be a game-changer for Lambda functions. Traditional Java has a reputation for slow startup, but GraalVM was designed to optimize that. For Lambda, which often handles quick tasks, GraalVM can start up and finish the job even before the standard JVM is fully booted.
While I haven’t directly worked with Java on Lambda before, I've learned that when dealing with numerous dependencies, using Lambda Containers can ease a lot of the pain. They allow your build environment to mirror the runtime environment, preventing mismatches that complicate the deployment. Plus, you get a much larger package size than the typical 250 MB limit. Just don't forget to set up your event handler correctly in the Dockerfile.

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