Afraid of Java cold starts in Serverless Fear not, Java is super fast!

For years, we’ve been told that Java suffers from cold starts in AWS Lambda and Serverless in general. Believe it not. Java is extremely fast to start, the simplest Java program starts in milliseconds. It’s the Java frameworks and libraries that slow things down in general. But not all of them… In this session, I want to show you the truth about Serverless Java and cold starts, what’s slow, what’s fast and why it matters. We’ll go through what a cold start is, how cold starts in AWS Lambda impact your application responsiveness and cloud costs, and what are the options to optimize both. We’ll explore and compare Quarkus and Piranha Cloud, the most modern and fastest Jakarta EE frameworks. We’ll test the limits of what they are capable of, how fast they start and whether we even need to think about any optimizations. Then I’ll explain what optimizations may help if you need to go further, like tuning the JVM, using a custom JVM runtime or building a OS-native binary with GraalVM. However, there are also a few limitations and cost implications of these optimizations, which we’ll also explain. I’ll show and tell, with very few slides. You’ll see live for yourselves how Java AWS Lambda functions built with Jakarta EE can start fast and decrease the cold starts to the absolute minimum which you can barely notice