Comparing Tomcat and Undertow in Spring Boot: Performance and Memory Usage

In the Spring Boot framework, Tomcat is the default embedded servlet container, but developers can replace it with Undertow, which offers better performance and lower memory usage.

Spring Boot is a popular Java web framework that simplifies project setup and embeds Tomcat as its standard container, providing essential web server capabilities for any web application.

To use Undertow, you only need to add the Undertow dependency to your project; the article includes images illustrating the required configuration steps.

Replacing Tomcat with Undertow can improve performance, especially under high‑concurrency workloads.

Tomcat, an Apache‑licensed lightweight servlet container, supports Servlet, JSP, and includes an HTTP server, while Undertow, a Red Hat open‑source project written in Java, offers both blocking and non‑blocking I/O, full Servlet and WebSocket support, and excels in high‑concurrency scenarios.

The article presents benchmark results comparing Tomcat and Undertow on the same hardware, showing QPS and memory usage charts:

The tests show that Undertow outperforms Tomcat in both throughput and memory consumption, especially for high‑concurrency business systems, making it the preferred choice for such scenarios.

In conclusion, Spring Boot allows the use of either Tomcat or Undertow as the HTTP server, and for high‑traffic applications, Undertow provides better performance and resource efficiency.