> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mcp-use.com/llms.txt
> Use this file to discover all available pages before exploring further.

# In-Memory Storage

> Use in-memory session storage for single-instance TypeScript MCP servers.

Use `InMemorySessionStore` when one server instance can own all session metadata and losing sessions on restart is acceptable. It stores session metadata in a JavaScript `Map`, so it has no external dependency and no persistence.

This guide focuses on when to use in-memory storage. Use the [Sessions API reference](/typescript/api-reference/server/sessions#inmemorysessionstore) for exact method behavior and the `SessionStore` contract.

## Use it for simple single-instance servers

In-memory storage is the production default when you do not pass a custom `sessionStore`. It is a good fit for small deployments, local prototypes, and services where clients can reconnect after a restart.

```typescript theme={null}
import { MCPServer, InMemorySessionStore } from "mcp-use/server";

const server = new MCPServer({
  name: "single-instance-server",
  version: "1.0.0",
  sessionStore: new InMemorySessionStore(),
});

await server.listen(3000);
```

You can omit `sessionStore` in production when in-memory storage is the behavior you want.

## Know what is stored

Session storage keeps serializable session metadata, such as client capabilities, client info, protocol version, log level, and access timestamps. It does not persist active transports, stream controllers, or runtime objects.

In-memory storage means:

* Sessions disappear when the process restarts.
* Other server instances cannot read the same sessions.

The default stream manager is also in-memory. That separate default means server-to-client workflows only reach clients connected to the same instance.

## Choose another store when sessions must survive

Use a different store when your deployment needs persistence or distribution.

| Need                                 | Use                                                                             |
| ------------------------------------ | ------------------------------------------------------------------------------- |
| Hot reload during local development  | [File System Storage](/typescript/server/session-management/filesystem-storage) |
| Load-balanced or distributed servers | [Redis Storage](/typescript/server/session-management/redis-storage)            |
| Durable metadata outside the process | Redis or a custom `SessionStore`                                                |

For distributed notifications, resource updates, or responses to server-to-client requests such as sampling and elicitation, a shared `sessionStore` is not enough. Configure a distributed `streamManager` as well.

## Verify the behavior

Use this store when these checks are acceptable:

* Restarting the server creates fresh sessions.
* A single process handles each connected client.
* You do not need to route server-to-client messages across instances.

If any check fails, choose file system storage for development persistence or Redis for distributed deployments.

## Next steps

<CardGroup cols={2}>
  <Card title="File System Storage" icon="folder" href="/typescript/server/session-management/filesystem-storage">
    Keep sessions across hot reloads in local development.
  </Card>

  <Card title="Redis Storage" icon="https://mintcdn.com/mcpuse/C8kWie3B44RcXcXB/images/icons/redis.svg?fit=max&auto=format&n=C8kWie3B44RcXcXB&q=85&s=869eede652ffc650a7ccd0734ed72c68" href="/typescript/server/session-management/redis-storage" width="24" height="24" data-path="images/icons/redis.svg">
    Share session metadata and streams across server instances.
  </Card>

  <Card title="Sessions API reference" icon="terminal" href="/typescript/api-reference/server/sessions">
    Look up session store methods, defaults, and contracts.
  </Card>

  <Card title="ServerConfig API reference" icon="server" href="/typescript/api-reference/server/server-config">
    Look up `sessionStore` and `streamManager` configuration.
  </Card>
</CardGroup>