Although Java has been a leader in enterprise applications for years, it receives criticism regarding memory consumption. This situation, which directly affects costs especially on VDS and cloud servers, is radically changing with GraalVM Native Image. So how does this technology work and how much does it save in real life?
What is GraalVM Native Image?
Traditional Java applications run on the JVM and execute bytecode by interpreting or compiling it just-in-time (JIT). In this process, the JVM itself, class loaders, GC infrastructure, and many other components take up memory. GraalVM Native Image offers a completely different approach: it pre-compiles (AOT) your application and its dependencies into a single native binary, eliminating the need for a JVM.
How Much RAM Savings?
Consider a small Spring Boot REST API. While it consumes about 200-300 MB of RAM initially with a standard JVM, the Native Image version of the same application can run with only 20-30 MB. This difference is particularly significant in microservice architectures. For example, in a system with 10 microservices, if each service consumes 30 MB instead of 100 MB, you achieve a total savings of nearly 700 MB. This can drastically reduce your monthly server costs.
Case Study: In our tests on HostingServer.com.tr, an e-commerce application's RAM usage dropped from 512 MB to 48 MB. Initial response times also decreased from 2.3 seconds to 0.1 seconds.
Advantages and Disadvantages
The fast startup and low memory consumption provided by Native Image are ideal especially in container environments. Faster pod startup in Kubernetes reduces autoscaling costs. But it's not all rosy: Build times are long (10-15 minutes in some projects), special configuration is required for Java's dynamic features (reflection, proxy), and since there is no JIT optimization, native code may not offer all speed advantages in long-running operations.
When Should You Use It?
- Short-lived processes – Ideal for serverless environments like AWS Lambda.
- Microservices – Standalone services with few dependencies.
- High-density container deployments – To run more services on the same node.
For long-running applications with complex frameworks (e.g., those using shared sessions), the classic JVM may still be more suitable for now. GraalVM Native Image does not yet fully cover the entire Java ecosystem, but compatibility is improving with each release.
Optimization Tips
Points to consider when converting a Java application to Native Image:
- Remove unnecessary dependencies. Native Image does not include unused classes.
- If you use reflection, declare the required classes in a reflection-config.json file.
- Examine Garbage Collector options: serial GC is the default, but you can enable G1 GC for lower latency (at the cost of additional memory).
- Try -O2 or -O3 optimization levels during compilation to improve performance.
In conclusion, GraalVM Native Image removes the biggest obstacle standing in Java's way, especially in hosting environments where RAM is precious. When balancing cost, speed, and resource usage, I highly recommend considering this technology.