Scheduled maintenance windows are a legacy habit, not a technical requirement. Here's the migration pattern we use instead.
Every migration plan starts with someone asking for a maintenance window. Most of the time, they don't actually need one — they need a rollback plan they trust.
The strangler-fig pattern lets you run old and new systems side by side, shifting traffic gradually behind a routing layer, validating the new path against shadow traffic before a single real customer touches it.
The unlock isn't the pattern itself — it's investing in observability early enough that you can tell, within seconds, whether the new path is behaving. Without that, no migration pattern will save you.