Serverless applications on AWS with Lambda using Java 25, API Gateway and Aurora DSQL – Part 7 Lambda performance optimization approaches

To find a good balance between the cold and warm start times of the Lambda function, you can try out the optimization techniques introduced below. I have not taken any additional measurements with our sample application with Java and GraalVM 25, but have done so using older Java, GraalVM, and dependency versions. I’ll provide references to my relevant articles. Measurements that I did back then might already be outdated, so I strongly recommend that you re-measure.

We can apply the following approaches to the managed Java runtime, Docker Container Image, and GraalVM Native Image. For the managed Java runtime and Docker Container Image, this includes enabling SnapStart and applying the priming techniques on top:

• Try out different Lambda memory settings. We performed all measurements with 1024 MB of memory for the Lambda function. With different memory settings, you might get a better price-performance trade-off. See my article Measuring cold and warm starts and deployment time with Java 21 using different Lambda memory settings for further examples, performance measurements, and conclusions.
• Try out setting arm64 architecture using the AWS Graviton2 processor, which supports SnapStart since July 2024. This can provide a better cost-performance trade-off compared to x86 architecture. See my article AWS Lambda performance with Java 21: x86 vs arm64 – Initial measurements for some insights.

We can apply the following approaches only to the managed Java runtime and Docker Container Image. This includes SnapStart being enabled and applying the priming techniques on top:

• Try out different Java compilation options for the Lambda function. We performed all measurements until now with the compilation option “-XX:+TieredCompilation -XX:TieredStopAtLevel=1”. We can provide other compilation options to the Lambda function using an environment variable called JAVA_TOOL_OPTIONS. This can have different cold and warm start trade-offs. For GraalVM Native Image, the choice of Java compilation method doesn’t have much impact on the Lambda performance. This is because our application is already compiled natively.
• Further exclude unused dependencies. With that, we can especially reduce the cold start times (also for SnapStart enabled). In the case of GraalVM Native Image, only reachable Java classes, functions, and methods will become a part of the Native Image, so including unused dependencies may not help that much.
• Search for further Lambda SnapStart priming potential in addition to those we introduced in this series. For this, you can use the AWS Lambda Profiler Extension for Java. I described it in my article Improving Lambda performance with Lambda SnapStart and priming.

We can apply the following approach primarily to the Docker Container Image :

• You can use Ahead-of-Time (AOT) and CDS caches for the Container Image and then measure the Lambda performance.

We can apply the following approach primarily to the GraalVM Native Image :

• Try out Profile-Guided Optimizations to see whether you can further improve Lambda performance. The difficulty of trying out this technique is that you’ll need to do some additional semi-automated steps to run your application either with the Lambda emulator locally or in an extra environment to obtain the profile of your application, which you’ll then need to use to generate the optimized Native Image. You can use Lambda extension for it, but it still requires a lot of additional work. This is the work AWS did for us in case Lambda SnapStart is enabled. I really appreciate that I don’t need to care about generating, encrypting, storing, and restoring the snapshots/profiles.