Why Switch to Undertow? Boost SpringBoot Performance Over Tomcat

Introduction

SpringBoot uses Tomcat as its default embedded container, but Undertow offers better performance and lower memory usage. This article explains how to replace Tomcat with Undertow in a SpringBoot project.

Tomcat Container in SpringBoot

SpringBoot is a popular Java web framework that simplifies creating web services. The embedded Tomcat container is the most commonly used servlet container in SpringBoot applications.

Configuring Undertow in SpringBoot

To use Undertow, add the Undertow starter dependency to the project (as shown in the image). After rebuilding, the application runs with Undertow instead of Tomcat.

Tomcat vs. Undertow Comparison

Tomcat is a lightweight servlet container from the Apache foundation, supporting Servlet and JSP, and includes an HTTP server. Undertow, developed by Red Hat, is a high‑performance, flexible Java‑based web server that supports blocking and non‑blocking I/O, servlet, and WebSocket.

Benchmark tests on identical hardware show that Undertow achieves higher QPS and lower memory consumption than Tomcat.

1. QPS Test Results

Tomcat

Undertow

2. Memory Usage Comparison

Tomcat

Undertow

The tests indicate that in high‑concurrency scenarios Undertow outperforms Tomcat in both throughput and memory efficiency, and its default use of persistent connections further improves performance.

Conclusion

Both Tomcat and Undertow can serve HTTP in SpringBoot, but Undertow delivers superior performance for high‑traffic systems, making it a recommended choice for such workloads.