Strangler Migration Versus Big-Bang Cutover
TradeoffStaffPrincipalUpdated
You're moving a billing system that processes $2M a day off a 12-year-old monolith onto new services. It exposes 40 endpoints, and finance allows at most one hour of billing downtime per year.
Short answer: Strangler Migration. Route traffic through a facade and move one endpoint at a time, so each piece proves itself under real load and can roll back on its own.
The Two Options
A
Strangler Migration
B
Big-Bang Cutover
Drill This: Your Pick First
The Better Pick
Option A
Strangler Migration
Route traffic through a facade and move one endpoint at a time, so each piece proves itself under real load and can roll back on its own. A big-bang cutover puts all 40 endpoints and every undocumented edge case into one weekend, and a single miss spends the downtime budget for the year. The strangler path also delivers value from the first endpoint moved.
When the Other One Wins
Big-Bang Cutover
When the old and new systems cannot run side by side, such as a vendor contract that ends on a fixed date or a data model that can't be dual-written, a rehearsed big-bang cutover is the safer plan.