Auto scaling question

New to Mongo Atlas. Is there a way to set the auto scaling (say M20 to M30) to happen in less than an hour? We have a transactional based system that uses Mongo, and an hour of CPU issues would be an issue for the system. Ideally I’d like to set something that if it spikes to 95% say 3 times in 5 minutes it scales up, then if it’s quiet for 2 hours is scales back down.

Hi Dennis! I’m a product manager on the Atlas team here at MongoDB. First of all, welcome to the platform - we’re glad to have you. For context, there is no way to configure how long it takes to auto-scale because Atlas handles all the resources on the backend and scales up as quickly as possible. Our system checks for 75%+ CPU and RAM utilization within an hour before scaling up, and 50%- CPU and RAM utilization within 24 hours before scaling down.

You can read more about the specifics of how auto-scaling works here: https://www.mongodb.com/docs/atlas/cluster-autoscaling/

However, I’d love to better understand your use case for your application as we’re always working on improving our auto-scaling functionality. If you’re open to it, send me an email at lori.berenberg@mongodb.com so we can learn more and ensure your feedback gets surfaced.

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Hi Lori,

We are using Mongo for the back end of a OLTP system that is 24/7. If the system needs a resource increase, waiting an hour to get those resources via automation could mean the system is overwhelmed until it scales up, so having the ability to set a faster scale up time would be beneficial in our scenario.

Thanks Dennis! Would you say that the time to trigger is more important than the actual time it takes to scale? And what is your tolerance for unnecessary scaling as a result of false bursts in activity? (i.e. a 5 minute burst that immediately goes back down within 10 mins)

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I’d think that for OLTP if it sees a sustained bust of X CPU or memory % (settable, but I’d think 85% would be what we would set) 2 minutes start the scaling and maintain it until there is an hour of activity that is reduced enough to trigger a scale down.