Comparing Tomcat and Undertow in SpringBoot: Performance, Memory Usage, and Deployment Guide

Preface

In SpringBoot the default embedded servlet container is Tomcat, but Undertow can be used as a replacement offering better performance and lower memory usage.

Tomcat Container in SpringBoot

SpringBoot is a popular Java web framework that simplifies project setup by eliminating XML configuration and providing an embedded Tomcat server for running web services.

Setting Undertow in SpringBoot

To switch from Tomcat to Undertow, add the Undertow starter dependency to the project; after rebuilding, the application runs with Undertow as the embedded server.

After configuration, the application starts with Undertow.

Why Replace Tomcat with Undertow?

Undertow, developed by Red Hat, is a lightweight, high‑performance Java web server that supports both blocking and non‑blocking I/O, servlet, and WebSocket, and generally outperforms Tomcat under high concurrency.

Tomcat vs Undertow Comparison

Benchmark results show that Undertow achieves higher QPS and lower memory consumption compared with Tomcat on the same hardware.

QPS comparison (image)

Memory usage comparison (image)

Conclusion

Both Tomcat and Undertow can serve HTTP in SpringBoot, but for high‑concurrency scenarios Undertow provides superior performance and should be considered as the preferred container.