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

# Memory Resident (MB), MongoDB

> Memory Resident (MB) for MongoDB deployments. Tracked live in Vortex IQ Nerve Centre. How to read it, why it matters, and how to act on it.

**Card class:** [Non-Hero](/nerve-centre/overview#card-classes-explained)  •  **Category:** [Capacity](/nerve-centre/connectors#connectors-by-type)

## At a glance

> **Memory Resident (MB)** is the amount of physical RAM the `mongod` process currently has resident, read live from the server. It is a capacity signal: it shows how much real memory the database is holding, which over time tells you whether the working set still fits in RAM or is pushing against the host's limit. Read it as a trend against your host's total memory rather than as a pass/fail number.

|                    |                                                                                                                             |
| ------------------ | --------------------------------------------------------------------------------------------------------------------------- |
| **What it tracks** | Resident physical memory held by the `mongod` process, in megabytes.                                                        |
| **Data source**    | `mem.resident` from `serverStatus`.                                                                                         |
| **Time window**    | `RT` (real-time, refreshed every 60 seconds).                                                                               |
| **Alert trigger**  | None by default. This is a trend and context card; pair it with the WiredTiger cache and disk cards for the alerting layer. |
| **Roles**          | owner, platform, sre, dba                                                                                                   |

## What it tracks

The card reports `serverStatus.mem.resident`, the resident-set size of the `mongod` process expressed in megabytes. This is the real physical memory the process holds right now, distinct from virtual memory (`mem.virtual`) and from the WiredTiger storage-engine cache, which is a configured subset of this footprint. On the WiredTiger storage engine, resident memory tends to grow toward a steady plateau as the cache fills with the working set, then stays roughly flat: that plateau is healthy. The number is most useful as a trend read against the host's total RAM. Resident memory sitting close to physical RAM, especially alongside a falling [WiredTiger Cache Hit Rate %](/nerve-centre/kpi-cards/mongodb/wiredtiger-cache-hit-rate), is the early sign that the working set no longer fits in memory and reads are spilling to disk. A single instantaneous value means little; the shape over hours and days is what matters.

## Reconciling against the source

Confirm the figure in MongoDB's own tooling with `db.serverStatus().mem.resident` in `mongosh`, or watch the `res` column in `mongostat`. On Atlas, the **Metrics** tab exposes a **System Memory** / process-memory chart for the same series. Expect small differences from operating-system tools such as `top` or `ps` (which may report the resident set at a slightly different instant or rounding), and remember the value is per-`mongod`, normally the primary.

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### Tracked live in Vortex IQ Nerve Centre

*Memory Resident (MB)* is one of hundreds of KPI pulses Vortex IQ tracks across MongoDB and 70+ other ecommerce connectors. Nerve Centre runs the detection layer; Vortex Mind investigates the cause when something moves; Ask Viq lets you interrogate any number in plain English.

[Start for free](https://app.vortexiq.ai/login) or [book a demo](https://www.vortexiq.ai/contact-us) to see this metric running on your own data.