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I'm working on setting up scaling policies for an ASG application.

I'm wondering if it is possible (or advisable) to combine Predictive and Dynamic scaling policies for a single ASG.

The peaks for the application load will be relatively cyclical, which should work well for Predictive Scaling. However there could be situations where the load is unusually high during particular events.

What I would like to do, is have the group scale based on forecasts, but also have the ability to scale in response to dynamic unexpected load.

What I want to avoid though, is a situation where the scaling policies are conflicting with each other. For example, the predictive scaling scale-down during heavy load times, because the forecast predicted low load.

It seems it would be easy enough to prevent problematic conflicts. For example, it could scale up if either of the policies, dynamic or predictive, indicated that additional capacity is needed, but only scale-down when both policies show that it's safe to do so.

Can anyone tell me if the scaling policies work in this way when combined. The documentation is fairly clear about how they work in issolation, but doesn't seem to mention what happens if they're combined.

user1751825
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  • i'd also like to know this because ["If actual capacity is greater than the predicted capacity, Amazon EC2 Auto Scaling doesn't scale in capacity."](https://docs.aws.amazon.com/autoscaling/ec2/userguide/ec2-auto-scaling-predictive-scaling.html#as-how-predictive-scaling-works) makes predictive scaling pretty effing niche in isolation – Cory Mawhorter Jun 01 '22 at 00:46
  • @CoryMawhorter I setup an application using both predictive and dynamic scaling, but it was just prior to moving to another company, so I don't actually know how well it's working. Next time I'm talking to someone from my old work, I'll enquire about it and provide an update here. – user1751825 Jun 01 '22 at 05:16
  • thanks for the followup -- i ended up going with Target scaling, which amazon describes as being "like your thermostat" i.e. it's always too hot or too cold. hey amazon -- i wish predictive did both – Cory Mawhorter Jun 12 '22 at 16:59

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