Strangler-fig migrations, contract testing, and observability — how we replace the engine mid-flight for systems that can't afford downtime.
You can't power down the systems that run payments, cases, or critical operations to rebuild them. Modernization has to happen with the engine running — which means the migration plan matters as much as the target architecture.
Strangle, don't replace
The strangler-fig pattern routes slices of traffic to new components while the old system keeps serving the rest. Each slice is validated in production before the next one moves, so risk stays small and reversible at every step.
Make behavior provable
Contract tests pin the behavior the rest of the organization depends on, and observability shows whether the new path matches the old one under real load. Together they turn a scary rewrite into a sequence of boring, verifiable steps.
- Route traffic incrementally; validate each slice
- Pin dependencies with contract tests
- Compare old vs. new under real load