[shireboy]

Microsoft calls this the strangler fig pattern and recommends it for large migrations: https://martinfowler.com/bliki/StranglerFigApplication.html

They make it somewhat easy to do using Yet Another Reverse Proxy (YARP). I’m in the middle of it for a .NET 4 to 6 migration. The challenge for me is that it introduces complexity. Developers have to think “do I fix this bug in v1 code or v2?” We have to host two backends instead of one. They both touch the same db, so that adds complexity- what if v2 does something in data that breaks v1? All solvable problems but just thought I’d share a from the trenches take. I do still think it is the right approach for this scenario.

[jollyllama]

Agreed. I've seen steel thread used to refer to a technique in developing new applications. In this context, it means building one feature to completion before starting others. For example in web development, build a screen that uses a route and an api endpoint to fetch data from your datastore before building other screens using only mocks.

Edit: the advantage of this is that any systemic problems will become apparent quicker; your earlier tasks become a proof of concept for the viability of the project as a whole.

[robertlagrant]

That sounds like vertical slices.

[jollyllama]

I hadn't heard of that term before but yes it is accurate.