> For the complete documentation index, see [llms.txt](https://docs.contextual.io/documentation-and-resources/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.contextual.io/documentation-and-resources/components-and-data/agents/scale-and-performance/event-lag-scaling.md).

# Event Lag Scaling

Event Lag Scaling automatically increases the number of processing Agent Instances you have based on the backlog of unprocessed events or messages. In the example below, the Agent is set to scale up to 3 instances if the number of unprocessed events exceeds 100. Events are added to Event Agents from Triggers, Actions and Send to Agent Nodes.

<figure><img src="/files/PRqh1X6yLfDGiAgPs0VU" alt=""><figcaption></figcaption></figure>

The **Event Lag Threshold** affects more than auto-scaling. It also governs how many messages should be buffered for each instance from the backlog at a time, which is what makes backlog work spread evenly across your running instances. See [Message Distribution](/documentation-and-resources/components-and-data/agents/how-agents-work/message-distribution.md) for details.


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