# Autoscaling

Source : https://webgune.cloud/en-us/docs/autoscaling · Mis à jour le 2026-10-27

# Autoscaling

Autoscaling automatically adjusts the number of instances (replicas) of a service based on its CPU load: more traffic, more instances; a lull, back to the minimum.

## Enabling autoscaling

In the service panel, **Observability / Scaling** tab:

| Parameter | Role |
|-----------|------|
| **Min** | Floor number of instances (never fewer) |
| **Max** | Ceiling on instances (never more) |
| **CPU target (%)** | Average utilization threshold that triggers adjustment |

Example: min 1, max 4, target 70%. If the average CPU across instances exceeds 70%, an instance is added (up to 4). Once the load drops back down for a sustained period, the excess instances are removed (down to 1).

## Manual scaling

Without autoscaling, you set the number of replicas by hand in the same tab. Going from 1 to 2 instances doubles capacity *and* adds redundancy: an instance restart no longer takes the service down.

## Application-side prerequisites

Multiple instances of your application run **in parallel** behind the same domain. Your code needs to be ready for this:

- **No in-memory state** shared across requests (sessions, local caches): externalize it to [Redis](/docs/db-redis) or the database.
- **Uploads and files**: write to a [persistent volume](/docs/volumes-persistants) or object storage, not to the instance's local filesystem.
- **WebSockets** work, but a client is connected to *one* instance: broadcast messages across instances via Redis pub/sub if needed.

## Choosing the right CPU target

- **70%** is a good default: enough margin to absorb a spike while an instance starts up.
- A target that's too low (30%) scales too early and costs resources; too high (90%), the service saturates before reinforcement arrives.
- Watch actual behavior in the service metrics after enabling it.

> The maximum number of instances remains bounded by your plan's limits (see [Limits and resources](/docs/limites-ressources)).