Producers must respect consumer speed — streams, SSE, WebSocket flood, rapid setState from socket.

Concurrency & Streams

Backpressure handling

<h2>Summary</h2>
<p>Same as <a href="#29-tearing-in-concurrent-ui">2.9 Tearing</a> at pipeline level — external store read mid-render shows inconsistent UI. Fix with <code>useSyncExternalStore</code>, versioned snapshots, or blocking render for legacy stores. Test fast scroll + live updates under Strict Mode.</p>
<h2>Code example</h2>
<pre><code class="language-javascript">const snapshot = useSyncExternalStore(
  store.subscribe,
  () =&gt; store.getSnapshot(),
);
// Consistent read for entire render pass
</code></pre>
<h2>Key points</h2>
<ul>
<li>Same as <a href="#29-tearing-in-concurrent-ui">2.9 Tearing</a> at pipeline level — external store read mid-render shows inconsistent UI.</li>
<li>Fix with <code>useSyncExternalStore</code>, versioned snapshots, or blocking render for legacy stores.</li>
<li>Test fast scroll + live updates under Strict Mode.</li>
</ul>
<h2>Further reading</h2>
<ul>
<li><a href="https://react.dev/reference/react/useSyncExternalStore">useSyncExternalStore</a></li>
<li><a href="https://react.dev/blog/2022/03/29/react-v18">Concurrent rendering</a></li>
</ul>
<h2>Related concepts</h2>
<ul>
<li><a href="/blogs/level-8-scheduler-internals">Scheduler internals</a></li>
<li><a href="/blogs/level-8-backpressure-handling">Backpressure handling</a></li>
</ul>


Same as [2.9 Tearing](#29-tearing-in-concurrent-ui) at pipeline level — external store read mid-render shows inconsistent UI.

Concurrent rendering tearing

React Scheduler (and browser `scheduler.postTask`) coordinate with `isInputPending` — cooperative multitasking.