Add docs on self-hosted ISR persisting across pods.

docs/basic-features/data-fetching/incremental-static-regeneration.md

@@ -171,6 +171,29 @@ export async function getStaticProps() {
 }
 ```
 
+## Self-hosting ISR
+
+Incremental Static Regeneration (ISR) works on [self-hosted Next.js sites](/docs/deployment.md#self-hosting) out of the box when you use `next start`.
+
+You can use this approach when deploying to container orchestrators such as [Kubernetes](https://kubernetes.io/) or [HashiCorp Nomad](https://www.nomadproject.io/). By default, generated assets will be stored in-memory on each pod. This means that each pod will have its own copy of the static files. Stale data may be shown until that specific pod is hit by a request.
+
+To ensure consistency across all pods, you can disable in-memory caching. This will inform the Next.js server to only leverage assets generated by ISR in the file system.
+
+You can use a shared network mount in your Kubernetes pods (or similar setup) to reuse the same file-system cache between different containers. By sharing the same mount, the `.next` folder which contains the `next/image` cache will also be shared and re-used.
+
+To disable in-memory caching, set `isrMemoryCacheSize` to `0` in your `next.config.js` file:
+
+```js
+module.exports = {
+  experimental: {
+    // Defaults to 50MB
+    isrMemoryCacheSize: 0,
+  },
+}
+```
+
+> **Note:** You might need to consider a race condition between multiple pods trying to update the cache at the same time, depending on how your shared mount is configured.
+
 ## Related
 
 For more information on what to do next, we recommend the following sections: