Quarkus is a Java framework for Kubernetes. Key technology components surrounding it are OpenJDK HotSpot and GraalVM. Quarkus provides developers a unified reactive and imperative programming model to address a wider range of distributed application architectures.
GraalVM is a Java Virtual Machine for compiling and running applications written in different languages to a native machine binary. GraalVM Community Edition has varying support and licensing requirements.
Mandrel is a downstream distribution of GraalVM CE, supporting the same capabilities to build native executables but based on the open source OpenJDK. Mandrel aims to make GraalVM easy to consume by Quarkus applications by only including GraalVM CE components that Quarkus needs. Red Hat began commercial support for using Mandrel to build native Quarkus applications since the Quarkus 1.7 release in October 2020.
Quarkus was designed around the container-first and Kubernetes-native philosophy, optimizing for low memory usage and fast startup times.
As much processing as possible is done at build time, including taking a closed-world assumption approach to building and running applications. This optimization means that, in most cases, all code that does not have an execution path at runtime isn't loaded into the JVM.
In Quarkus, classes used only at application startup are invoked at build time and not loaded into the runtime JVM. Quarkus also avoids reflection as much as possible, instead favoring static class binding. These design principles aim to reduce the size, and ultimately the memory footprint, of the application running on the JVM while also enabling Quarkus to be natively-native.
Quarkus' uses the native image capability of GraalVM to compile JVM bytecode to a native machine binary. GraalVM aggressively removes any unreachable code found within the application's source code as well as any of its dependencies. Combined with Linux containers and Kubernetes, a Quarkus application runs as a native Linux executable, eliminating the JVM.
Quarkus rests on an ecosystem of technologies, standards, libraries, and APIs, including Contexts & Dependency Injection (CDI), Jax-rs, Java persistence api (JPA), Java Transaction API (JTA), Apache Camel, and Hibernate.
Quarkus is an Ahead-of-time compilation (AOT) platform, optimizing code for the JVM as well as compiling to native code for improved performance. All of the underlying technologies are AOT-enabled.