> ## 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 Replicas, MySQL

> Active Replicas for MySQL 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:** [Replication](/nerve-centre/connectors#connectors-by-type)

## At a glance

> **Active Replicas** is the count of replica servers currently attached to this MySQL source and streaming changes from it. It is the simplest health check on your replication topology: if the number drops below what you expect, a replica has disconnected and your read-scaling or failover headroom has shrunk. The value is sampled in real time so a dropped replica shows up within one refresh cycle.

## What it tracks

The card counts the replicas a source server can see, typically from `SHOW REPLICAS` (formerly `SHOW SLAVE HOSTS`) on the source, or from the replica-side connection registry. A replica appears here while its IO thread holds an open connection to the source and is registered with a server ID. The expected number is whatever topology you designed: a single read replica reads 1, a three-node read pool reads 3, and so on. A reading below your baseline means a replica process has stopped, lost its network path, or been deliberately detached. The card has no alert threshold of its own (`time window: RT`); it is a context number you read alongside the lag and thread-health cards, which carry the alerts.

**Reconcile against the source:** run `SHOW REPLICAS;` on the source instance, or compare against the replica roster in your managed-service console (for example the Amazon RDS read-replica list or the Aurora cluster members view).

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### Tracked live in Vortex IQ Nerve Centre

*Active Replicas* is one of hundreds of KPI pulses Vortex IQ tracks across MySQL 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.