[smarx007]

What you are missing are the Amazon API Gateway costs. I really liked my own calculations on Lambda costs similar to yours until I figured I'd need to use API Gateway too.

Edit: another thing is the amount of RAM used by functions. The CPU speed you get is proportional to RAM so if your code fits in the RAM but has poor performance, doubling the RAM is what you have to do. Another hidden cost.

[oppopower]

Thanks, peer review is what I'm after

The GB/sec calc is there My assumption was that even with k8s there'll be an API gateway, GTM etc

Comparing AWS Lamda = 147,167.87 USD to K8s with autoscaling:

DS32a_v4 at spot pricing = 66 * 0.5704 * 24 * 365 = 329782.46 USD With 2 FTEs @ 100k total is 529782.46 USD Caveat application can tolerate autoscaling delays

Summary: AWS Lambda is 3.5x cheaper than a Kubernetes solution

[dougmoscrop]

The calculations are still a little more complicated. I think serverless is the future, but I also think we need to continue to put pressure on AWS to lower costs

Lambda and servers are not equal, you can't just calculate the number of servers one would need for an equivalent Lambda load. It's entirely possible that they could get away with significantly fewer servers than you think.

Your cost calculation includes 128mb provisioned. You cannot run an API with 128mb Lambdas. Try 1gb or even 1.5gb. It's not that you need that much memory of course, but if you want to have p98 execution and initialization times that are palatable, you need the proportional speed benefits that come with the additional memory.

And no, you won't need API gateway because you'd likely be including your own in your cluster and it will handle far more load without needing nearly as much autoscaling as the app servers.

Lambda autoscales too - it's not instant, and there are steps it goes through as it ramps up.

If Lambda removed the per-invocation overhead and billed for actual CPU time used, not "executing" (wall) time, I think that would be fantastic. Again, I still think it's the future, but it has a ways to go before it's appropriate for certain use cases and load profiles.

Edit: oh, and I think the managed ROI is also a case by case basis. Do you have people who know how to run a cluster for you already? Completely different conversation.

I will also say that Lambda is still not maintenance-free, either.

[plantain]

API gateway is optional though - it's poorly documented but most workloads are just fine without it.

[smarx007]

How does one invoke a Lambda function via HTTP without an AWS account (ie a public API call)? I think you are not including it in the "most workloads"?

[dougmoscrop]

Most if not all AWS services are really just HTTP APIs. A Lambda invocation is really just a POST to a public AWS endpoint. You can absolutely come up with login flows that obtain a set of temporary STS credentials that are only allowed to invoke your "API" function. (Agreed this is not most workloads)