the core and max pool size should be set to the same value - the JVM has a weird setting that it only starts to add more threads once the queue is full (which is 1000 for you).
However, if you’re using Spring Boot, make sure to use the right properties: have a look at this recent forum post: Flowable 7.2.0: Node Affinity Hoards All Jobs – All Async Jobs Locked by Node 1 while only 8 are being processed - #10 by ROY