Why Switch from Tomcat to Undertow in SpringBoot? Performance & Memory Benefits

Introduction

In the SpringBoot framework, Tomcat is the default embedded container, but SpringBoot also supports Undertow, which offers better performance and lower memory usage.

Tomcat Container in SpringBoot

SpringBoot is a popular Java web framework that lets developers create a complete web service within minutes, freeing them from heavy XML configuration. Web container technology is essential for any web project, and Tomcat is the most commonly used container.

Configuring Undertow in SpringBoot

To replace Tomcat with Undertow, simply add the Undertow dependency to the project. After adding the dependency and rebuilding, the application starts with Undertow as the embedded server.

Tomcat vs Undertow Comparison

Tomcat is an Apache lightweight servlet container that supports Servlet and JSP, includes an HTTP server, and is free. Undertow, developed by Red Hat, is a flexible high‑performance Java web server that supports blocking and non‑blocking I/O, embeds easily, and fully supports Servlet and WebSocket.

Performance Test Results

Under identical machine configurations, QPS and memory usage were measured. The results show that Undertow achieves higher QPS and lower memory consumption than Tomcat, especially under high concurrency. Undertow’s newer versions also use persistent connections by default, further improving throughput.

Conclusion

Both Tomcat and Undertow can serve HTTP in SpringBoot, but Undertow outperforms Tomcat in high‑concurrency scenarios. For systems with heavy request loads, switching to Undertow can significantly boost performance.