With the default configuration below, the keepalive-time does not have any effect and it is creating a new thread on every request even when there are idle threads.

        <subsystem xmlns="urn:jboss:domain:ejb3:1.5">
            ...
            <thread-pools>
                <thread-pool name="default">
                    <max-threads count="10"/>
                    <keepalive-time time="100" unit="milliseconds"/>
                </thread-pool>
            </thread-pools>
        </subsystem>