[phamilton]

I've always known how to do zero downtime migrations. The question has always been "Is the engineering cost worth it?"

> It only makes backwards compatible deployments easier insofar you're able to do the overhead for splitting the change with less effort then before.

Yes. That reduces the cost of implementing them.

To be clear, I'm not talking about "Split my db migration and my code that depends on the new table". I'm talking about things like "Set up dual writes between an old database schema and a new database schema with a thorough test suite and do shadow reads against both datasets in prod to do differential testing". That's nontrivial engineering effort that would definitely warrant a discussion in the past. Today we just do it. It's fast and lowers risk.