Is it a web service? Can you put a proxy in front of the old, to allow you to observe, and potentially duplicate (to the new, whilst testing) all requests that go to the old system?
If you're migrating data, can you take counts of things, so you can get quickly verify, i.e. we have 2.32M records before, and we have a way to prove we have 2.32M records after.
Mostly though, all migrations take longer than you think.
If you're migrating data, can you take counts of things, so you can get quickly verify, i.e. we have 2.32M records before, and we have a way to prove we have 2.32M records after.
Mostly though, all migrations take longer than you think.