[agavra]

There's a whole class of interesting problems related to query evolution - and it varies greatly depending on the "environment" that you're interested in (see mjdrogalis' docs on updating a running query). Generally, the strategy that ksqlDB takes at the moment is to validate what upgrades are possible to do in-place and which are not - for the former, ksqlDB "just does it" and for the latter, we are designing a mechanism to deploy topologies side-by-side and then atomically cut over when the new topology is caught up to the old one.

There's an in-progress blog post that describes exactly this class of problems - keep an eye out for it!