> ## 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.

# Active Readers, MongoDB

> Active Readers for MongoDB instances. 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

> **Active Readers** is the count of clients currently performing read operations on the MongoDB instance, read straight from `globalLock.activeClients.readers` in the `serverStatus` output. It is a real-time gauge of read concurrency: how many connections are actively holding or waiting on the read side of the global lock at the instant the sample is taken. A steady low number is normal; a sudden climb means read demand has spiked or reads are queuing behind a slow operation.

|                    |                                                                                                                                        |
| ------------------ | -------------------------------------------------------------------------------------------------------------------------------------- |
| **What it tracks** | The instantaneous number of active read clients on the instance, taken from `globalLock.activeClients.readers` in `db.serverStatus()`. |
| **Data source**    | MongoDB `serverStatus` command, `globalLock.activeClients.readers` field, polled in real time.                                         |
| **Time window**    | `RT` (real-time snapshot, refreshed on the live poll).                                                                                 |
| **Alert trigger**  | None. This is a diagnostic capacity signal, not an alerting card.                                                                      |
| **Roles**          | DBA, platform, SRE                                                                                                                     |

## What it tracks

Active Readers reports the value of `globalLock.activeClients.readers` at sample time. MongoDB tracks, for each instance, how many client connections are actively engaged on the read side of the global lock subsystem. This is a concurrency reading, not a throughput reading: it tells you how many reads are in flight right now, not how many completed over a window. Read it next to [Active Writers](/nerve-centre/kpi-cards/mongodb/connections-in-use) style capacity peers and [Operations per Second (live)](/nerve-centre/kpi-cards/mongodb/operations-per-second-live). A persistently high reader count alongside rising [Query Latency p95 (ms)](/nerve-centre/kpi-cards/mongodb/query-latency-p95-ms) usually means reads are backing up behind a long-running query or a cache miss storm, rather than healthy parallelism. Because the value is a single-moment snapshot, expect it to flicker between polls on a busy instance; trends matter more than any one reading.

## Reconciling against the source

To confirm the live figure, run `db.serverStatus().globalLock.activeClients.readers` in `mongosh` against the same node, or watch the `qr` (queued reads) and `ar` (active reads) columns in `mongostat`. On MongoDB Atlas, the same signal surfaces under the Metrics tab as the active reader count in the global lock charts. Small differences between our reading and a manual run are expected: both are point-in-time samples taken at slightly different instants.

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### Tracked live in Vortex IQ Nerve Centre

*Active Readers* 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.