> ## Documentation Index
> Fetch the complete documentation index at: https://auth0-docs-event-stream-action-templates.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

> How to cache expensive resources in your Rules code.

# Cache Expensive Resources in Rules

<Warning>
  The End of Life (EOL) date of Rules and Hooks will be **November 18, 2026**, and they are no longer available to new tenants created as of **October 16, 2023**. Existing tenants with active Hooks will retain Hooks product access through end of life.

  We highly recommend that you use Actions to extend Auth0. With Actions, you have access to rich type information, inline documentation, and public `npm` packages, and can connect external integrations that enhance your overall extensibility experience. To learn more about what Actions offer, read [Understand How Auth0 Actions Work](/docs/customize/actions/actions-overview).

  To help with your migration, we offer guides that will help you [migrate from Rules to Actions](/docs/customize/actions/migrate/migrate-from-rules-to-actions) and [migrate from Hooks to Actions](/docs/customize/actions/migrate/migrate-from-hooks-to-actions). We also have a dedicated [Move to Actions](https://auth0.com/extensibility/movetoactions) page that highlights feature comparisons, [an Actions demo](https://www.youtube.com/watch?v=UesFSY1klrI), and other resources to help you on your migration journey.

  To read more about the Rules and Hooks deprecation, read our blog post: [Preparing for Rules and Hooks End of Life](https://auth0.com/blog/preparing-for-rules-and-hooks-end-of-life/).
</Warning>

In Rules you can store expensive resources using the `global` object. The `global` object survives individual execution, so you can reuse things stored there instead of creating them every time a Rule is run. However, the Rules environment can be recycled at any time so your code **must** always check that `global` contains what you expect.

This example shows how to use the `global` object to keep a MongoDB connection:

```javascript lines theme={null}
//If the db object is there, use it.
if (global.db){
  return query(global.db, callback);
}

//If not, get the db (mongodb in this case)
mongo('mongodb://user:pass@mymongoserver.com/my-db',  function (db){
  global.db = db;
  return query(db, callback);
});

//Do the actual work
function query(db, cb){
  // Do something with db
  ...
  return cb(null, user, context);
}
```

To learn more about using MongoDB, read [the MongoDB Manual](https://docs.mongodb.com/manual/).