Is Azure Functions running in Consumption mode app

Question

I’m about to start work on an API that will literally go from 0 RPS to a couple hundred thousand HTTP RPS at the same time and run at that rate for ~2 mins. All processing of those 30 million requests must finish by the end of that 2 min period. This would happen 7 times a WEEK.

Going serverless with Azure Functions in Consumption Plan Hosting Mode sounds appealing. This document describes that a scale controller exists to coordinate app instances, but doesn't really discuss what I can expect from it for HTTP triggers. I can’t find any info that says the scale controller will be able to respond in the time frame I'd need.

The best info I could find was this info saying it took nearly 8 mins to scale up for his tests.

Is this a bad use case for Azure Functions in consumption mode?

Obviously, spinning up a testing harness that is capable of issuing 30 million requests within 2 minutes is an undertaking of its own, and an expensive one. I'd like to learn from others who have already done so.

Answer 1

Based on my experience, this scenario is not properly covered by Consumption Plan. They can scale up to many instances, but not very rapidly. 2 minutes is way too fast to rely on.

I was mostly working with queues, not HTTP, but I got delays up to 40 minutes caused by low pace of scaling up.

If you can predict which 2 minutes are going to be heavy-loaded, your best bet could be to provision the capacity with a script (or another Function).