Thank you for all the explanations. I think I have better understanding now. Another question, at what scale (in terms of number of services, and maybe throughput? what other dimensions?) should we start considering using temporal?

I think scale is less important than other considerations. For me the biggest motivator is when the use case prefers doing something exactly-once, the downside risk of failure is high, and robust failure handling is moderately complex. The canonical example I use is healthcare communications; others use payment/fulfillment.

Also having a unified control plane is handy even at a pretty small scale if your alternative is going full “cloud native” on hyperscaler microservices. The ability to see what’s happening when and where across a single workflow run is a dream compared to all the traditional logging approaches I’ve seen.