However, the real productivity killer is not system rewrites but the migrations that follow those rewrites. Poorly designed migrations expand the consequences of this rewrite loop from the individual teams supporting the systems to the entire surrounding organization.
If each migration takes a week, each team is eight engineers, and you’re doing four migrations a year, then you’re losing about 1 percent of your company’s total productivity. If each of those migrations takes closer to a month, or if they are only possible for your small cadre of trained engineers—whose time is already tightly contended for—then the impact becomes far more pronounced.
An Elegant Puzzle: Systems of Engineering. Will Larson.