Thank you for the reply. As you have said, it has nothing to do with the async executor. After some research, I found out that the mistake I made was using StandaloneInMemProcessEngineConfiguration in the spring boot application. That’s why flowable was not able to find the bean.
When I used SpringProcessEngineConfiguration to build the process engine, the service task is working fine.
Then another problem raised with Business Rule Task. I have opened another topic. Please see if you have any inputs on that.
Thanks.