Out of curiosity, have you explored the possibility of a serverless orchestration layer? That's one of the most appealing parts of Step Functions. We have many large workflows that run just a couple times a day and take several hours alongside a few short workflows that run under a minute and are executed more frequently during peak hours. Step Functions ends up being really cost effective even through many state transitions because most of the time, the orchestrator is idle.

Coming from an existing setup where everything is serverless, the fixed cost to add serverfull stuff feels like a lot. For a HA setup, it'd be 3 EC2 instances and 3 NAT gateways spread across 3 AZs. Then multiply that for each environment and dev account, and it ends up being pretty steep. You can cut costs a bit by going single AZ for non-prod envs, but still...

I couldn't find a pricing model for Restate Cloud, but I'm including "managed services" under the definition of serverless for my purposes. Maybe that offering can fill the gap, but then it does raise security concerns if the orchestration is not happening on our own infra.