Id</code>s by default. See
the section on <a href="#async_hooks_promise_execution_tracking">promise execution tracking</a>.</p>
<h2>Promise execution tracking<span><a class="mark" href="#async_hooks_promise_execution_tracking" id="async_hooks_promise_execution_tracking">#</a></span></h2>
<p>By default, promise executions are not assigned <code>asyncId</code>s due to the relatively
expensive nature of the <a href="https://docs.google.com/document/d/1rda3yKGHimKIhg5YeoAmCOtyURgsbTH_qaYR79FELlk/edit">promise i