> For the complete documentation index, see [llms.txt](https://docs.ionos.com/cloud/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ionos.com/cloud/~/revisions/AMiYziCllTKB2y2lmONY/databases/mongodb/overview/sizing.md).

# Sizing

{% hint style="info" %}
**Note:** Currently, DBaaS - MongoDB does not support scaling existing clusters.
{% endhint %}

### RAM

The WiredTiger cache uses only a part of the RAM; the remainder is available for other system services and MongoDB calculations. The size of the RAM used for caching is calculated as `50% of (RAM size - 1 GB)` with a minimum of 256 MB. For example, a 1 GB RAM instance uses 256 MB, a 2 GB RAM instance uses 512 MB, a 4 GB instance uses 1.5 GB, and so on.

You get the best performance if your working set fits into the cache, but it is not required. The working set is the size of all indexes plus the size of all frequently accessed documents.

To view the size of all databases' indexes and documents, you can use a similar script as described in the [MongoDB Atlas documentation](https://www.mongodb.com/docs/atlas/sizing-tier-selection/#example--the-service-sample-data-sets). You must estimate what percentage of all documents are accessed at the same time based on your knowledge of the workload.

Additionally, each connection can use up to 1 MB of RAM that is not used by WiredTiger.

### Disk

The disk contains:

* Logs written by [MongoD](https://www.mongodb.com/docs/manual/reference/program/mongod/) and [MongoS](https://www.mongodb.com/docs/manual/reference/program/mongos) (in case of a sharded cluster). They can take up to 2% of the disk space before MongoDB deletes them.
* OpLogs for the last 24 hours. The size of these depends on your workload. There is no upper limit, so they can grow quite large. But they are removed after 24 hours on their own.
* The data itself. Operating systems and applications are kept separately outside the configured storage and are managed by IONOS.

### Limitations

**Connection Limits:** As each connection requires a separate thread, the number of connections is limited to 51200 connections.

**CPU:** The total upper limit for CPU cores depends on your quota. A single instance cannot exceed 31 cores.

**RAM:** The total upper limit for RAM depends on your quota. A single instance cannot exceed 230 GB.

**Storage:** The upper limit for storage size is 4 TB.

**Backups:** Storing cluster backups is limited to the last 7 days. Deleting a cluster also immediately removes all backups of it.

**IP Ranges:** The following IP ranges cannot be used with our MongoDB services:

* `172.16.0.0/12`
* `192.168.230.0/24`


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.ionos.com/cloud/~/revisions/AMiYziCllTKB2y2lmONY/databases/mongodb/overview/sizing.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.