Infrastructure
A data migration is scoped by what the system can't do yet
A migration estimate prices the copy. Three capabilities the system had before the plan existed decide the rest, and whatever it lacks is the project.
Migration
Infrastructure
Your safe migration window closes before the deadline
Migration safety spends time: rehearsal, phased rollout, observation, rollback. Once the schedule can't afford them, the safe migration window has closed.
Infrastructure
Migrate one variable at a time, or you won't know what broke
Hold every variable but one and a failure has one suspect. Bundle two and the suspects grow like the subsets: three places to look, then seven.
Risk Management
The irreversible decisions go first
Most risks are prices you can pay. The one with no affordable way back is different. Settle those decisions first, while you still have a choice.
Infrastructure
Procedural risk shrinks; structural risk doesn't
Some risks shrink with effort. Others absorb the same investment and don't move. One question tells them apart during evaluation.
Risk Management
Why novelty, scale, and time compression fail together
One factor is mundane. Two are manageable. Three is where failure becomes systemic, because each removes the safety margin the other two need.
Migration
You can't roll back to a system you already changed
Mutation collapses rollback when you need it most. Coexistence keeps rollback available at every step by running old and new side by side.