I'm seeing a lot of buzz about GraalVM and Ahead-of-Time (AOT) compilation. For those of you running Spring Boot 3 in production, how much of a difference does a Native Image actually make in terms of startup time and memory footprint? Is the loss of JIT (Just-In-Time) optimization noticeable in long-running processes, or do the cloud-cost savings outweigh it?
3 answers
For containerized deployments, it's a no-brainer. Smaller images mean faster pulls and less money spent on idle RAM in your cluster.
The startup time difference is astronomical. We saw a Spring Boot service go from 12 seconds to 0.08 seconds. In a serverless environment like AWS Lambda or when using Kubernetes HPA, this is vital for scaling. Memory usage also dropped by about 60% since the JVM overhead is gone. However, be aware that JIT can eventually outperform AOT in throughput for very long-running heavy compute tasks because it optimizes based on runtime data. For most web APIs, the AOT performance is more than sufficient.
Does AOT compilation complicate the build pipeline? We use a lot of reflection in our custom frameworks, and I've heard GraalVM struggles with that.
Daniel, you're right that reflection requires 'reachability metadata.' However, Spring Boot 3 has an 'AOT engine' that generates this configuration for you automatically during the build. If you use custom reflection, you might need to provide a hints file, but the tooling has matured so much that it's no longer the manual headache it was two years ago.
Completely agree, Susan. We reduced our EKS cluster costs by nearly 40% just by switching our most frequently scaled services to native images.