I've created a bean pool to limit the number of some instances. In that case maximum 5 instances.

<pools>
<bean-instance-pools>
<strict-max-pool name="slsb-max5" max-pool-size="5" instance-acquisition-timeout="5" instance-acquisition-timeout-unit="MINUTES"/>
...
</bean-instance-pools>
</pools>

The idea was to have some async service that work simultaneous.

@Stateless
@Pool("slsb-max5")
public class AsyncService {
@Asynchronous
public Future<LocalDateTime> async2Seconds()

}

The problem is when I invoke simultaneous more than 5 times it blocks the threads even it is not using (async thread-pool-name="default", default=10)

Attached an example project (configure slsb-max5 pool and access /test-thread-pool/rest/async-resource)