[KraftyOne]

As the post says, the exactly-once guarantee is ONLY for steps performing database operations. For those, you actually can get an exactly-once guarantee by running the database operations in the same Postgres transaction as your durable checkpoint. That's a pretty cool benefit of building workflows on Postgres! Of course, if there are side effects outside the database, those happen at-least-once.

[tonyhb]

You can totally leverage postgres transactions to give someone... postgres transactions!

I just figured that the exactly once semantics were so worth discussing that any external side effects (which is what orchestration is for) aren't included in that, which is a big caveat.