I created a minimal example project which demonstrates the EJB timer issue. The project can found on https://github.com/cboehme/wildfly-timer-issue/ . Steps to reproduce Clone and build the wildfly-timer-issue project: git clone https: //github.com/cboehme/wildfly-timer-issue.git cd wildfly-timer-issue mvn clean package Start a clean Wildfly and configure the request controller to allow at max two requests. Additionally, debug logging for org.jboss.as.ejb3.timer should be enabled. The configure wildfly.cli Wildfly CLI script can be used to make this configuration automatically on a locally installed Wildfly. Deploy the request-maker application on the new wildfly. It is a simple web application with single endpoint /make-request that takes thirty seconds to complete a HTTP GET request. It enables us to clog up the request controller. Make two requests to http://localhost:8080/make-request in parallel. These requests will run for 30 seconds and take up all available requests on the Wildfly instance. While the two requests are running deploy the timer application on the same wildfly. This application defines an EJB timer which fires every five seconds. Its callback take one second to complete. The Wildfly console output shows that the timer application is deployed and that it registered an ejb timer. However, the callback method of the timer is never called. Not even after the two web requests have finished. Once the two web requests finished, log into the Wildfly admin interface and suspend and resume the server. Now the timer invocation will be processed and the timer starts working as expected. Now, try to make two more parallel requests to http://localhost:8080/make-request while the timer is running. If the timer is being activated just when the second request arrives, this request will be rejected (as expected) with a "503 - Service Unavailable". If the second request goes through, though, the timer stalls again until the requests finished and the server is suspended and resumed.