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Clarify which instance runs scheduled events when scaling to multiple instances #11749

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Clarify which instance runs scheduled events when scaling to multiple instances #11749

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8faf2bf
Clarify scheduled event distribution across multiple instances
Yornik Aug 17, 2026
0cc81d5
Apply style guide rules to the scheduled events note
Yornik Aug 17, 2026
c48beda
Correct the cause of uneven CPU usage in the scaling note
Yornik Aug 17, 2026
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3 changes: 2 additions & 1 deletion content/en/docs/deployment/mendix-cloud-deploy/scale-environment.md
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Expand Up @@ -15,7 +15,7 @@ This document explains how to scale an environment in Mendix Cloud. This can tak
* Horizontal scaling – You can configure apps built using supported versions of Mendix to be run in multiple runtime containers (instances) simultaneously. Incoming traffic for your app is distributed over the running instances.

{{% alert color="info" %}}
For versions below Mendix 9.12.0, [scheduled events](/refguide/scheduled-events/) are always run on the first instance if there are multiple instances.
If there are multiple instances, legacy [scheduled events](/refguide/scheduled-events/) are only executed on the [cluster leader](/refguide/clustered-mendix-runtime/#cluster-leader-follower), and task queue based scheduled events are executed on an arbitrary instance. For versions below Mendix 9.12.0, all scheduled events are always run on the first instance.
{{% /alert %}}

## Prerequisites
Expand Down Expand Up @@ -46,6 +46,7 @@ To scale your licensed app in Mendix Cloud, follow these steps:
* The number of available instances depends on the total memory provided by your cloud resource pack and the memory per instance that you have set. It is not possible to set scaling values that exceed the memory provided by your [cloud resource pack](/developerportal/deploy/mendix-cloud-deploy/#resource-pack).
* It is not possible for a single instance to use more than 32 GiB of RAM. Some very large cloud resource packs, such as XXXL21 or XXXXL21, provide more than this 32 GiB maximum; to use the full RAM in this case, you need more than one instance. For example, to use 64 GiB of RAM, you must spread the RAM between two or more instances.
* Consider the functionality that runs inside task queues; think about whether the scope of these task queues should be configured to run in all instances or once per cluster. It is possible to set the [scope of the threads](/refguide/task-queue/#create-queue) per task queue.
* Instances can show different CPU usage. For example, legacy scheduled events run only on the [cluster leader](/refguide/clustered-mendix-runtime/#cluster-leader-follower), so that instance can use more CPU than the others even when incoming traffic is distributed evenly.

## Examples

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