At first it looks easy to use any pub/sub or DB to create a job system, but there are so many edge cases, I'm not even talking about scaling etc ... just having a solid job system that properly handle retries, error, durability, timeout etc ...
Every 3rd party dependency is a complexity you must manage.
Every in house system is a complexity you must manage.
Nothing is free.
and on the Temporal side, not B2C directly, but serving large B2C. We now can cite Snap as a public customer - every Snapchat story runs through us (and yeah, theres not infinite spend for orchestration either so make of that what you will). and we have bigger users than Snap.
but we could add the ability for workflows to subscribe to kafka topics in future? no promises on the exact level of abstraction we’ll land on but its definitely been discussed