at are not serializable and cannot be transferred from the
JobManager&rsquo;s JVM.</p>
</li>
</ul>
<p>Most importantly, <code>ProcessFunction</code> also has access to the fault-tolerant
state, handled by Flink. This combination, together with Flink's
message processing and delivery guarantees, makes it possible to build
resilient event-driven applications with almost arbitrarily
sophisticated business logic. This includes creation and processing of
custom windows with state.</p>
<h3 id="implementation">
 