Overview
A B2B platform had grown into a tightly coupled backend where changes in one area often caused regressions in another.
Challenge
API behavior was inconsistent and historical quirks were relied on by multiple clients. A full rewrite was too risky for active product commitments.
Approach
We defined domain boundaries, introduced versioned contracts, and migrated risky paths gradually behind compatibility layers with contract checks.
Architecture
Core concerns were separated into clearer modules, with schema validation and API contract checks in CI to prevent drift.
Outcome
The team regained control of backend changes and could deliver features with fewer integration surprises.
Lessons
Refactors work best when migration sequencing and contract clarity are treated as core engineering work from day one.