Maximum (client request) thread pool size in spring

Assuming that you're using embedded Tomcat, Spring Boot uses the server.tomcat.max-threads property to control the size of the client request thread pool. Its default value is zero which leaves Tomcat to use its default of 200.

To customise the size of this thread pool you should specify a non-zero value for the server.tomcat.max-threads property in your application.properties or application.yml file.

As server.tomcat.max-threads is deprecated since Springboot 2.3, now use server.tomcat.threads.max in your Spring application.properties. Default is 200.