How to Migrate New Features?

Sometimes a new feature might require migrating data. The first thing is to ask yourself honestly if that's necessary, because sometimes it's not. If the new path doesn't work, fall back to pulling data from the old path and migrating it on demand. That's going to introduce some additional latency for people the first time they go through. But it prefers the new data if it's available. So i've usually seen this as kind of a three step process that i would love to have a name for.