We assessed Quarkus two years ago, and now our teams have more experience with it. Quarkus is a Kubernetes-native Java stack tailored for OpenJDK HotSpot and GraalVM. Over the past two years, Quarkus has wired those best-of-breed libraries in the Java world and streamlined the code configuration, giving our teams a pretty good developer experience. Quarkus has a very fast boot time (tens of milliseconds) and a low RSS memory footprint; this is because of its container-first building approach: it uses ahead-of-time compilation techniques to do dependency injection at compile time and thus avoids the run-time costs of reflection. Our team has also had to endure the trade-offs: it takes nearly 10 minutes for Quarkus to build on our pipeline; some features that rely on annotations and reflection (such as ORM and serializer) are also limited. Part of these trade-offs are the result of using GraalVM. So if your application is not running for FaaS, using Quarkus with HotSpot is also a good choice.
Quarkus is a cloud-native, container-first framework by Red Hat for writing Java applications. It has a very fast startup time (tens of milliseconds) and has low memory utilization which makes it a good candidate for FaaS or frequent scaling up and down in a container orchestrator. Like Micronaut, Quarkus achieves this by using ahead-of-time compilation techniques to do dependency injection at compile time and avoid the runtime costs of reflection. It also works well with GraalVM's Native Image which further reduces startup time. Quarkus supports both imperative and reactive models. Along with Micronaut and Helidon, Quarkus is leading the charge on the new generation of Java frameworks which attempt to address startup performance and memory without sacrificing developer effectiveness. It's gained a lot of community attention and is worth keeping an eye on.