Legacy Workflow Migration to a Backend API

Moving a business-critical workflow out of database procedures and into a layered .NET service — incrementally, without disrupting production.

C# / .NETSQL ServerREST APIsClean Architecture

Problem: A business-critical workflow depended on legacy database procedures and tightly coupled processing logic, making changes risky and difficult to troubleshoot. Failures were hard to isolate, and the synchronous flow made the system more fragile as the workload increased.
Approach: I migrated the workflow into a .NET backend service, separating orchestration, validation, persistence, and external integrations into clearer application layers. I considered keeping the logic primarily in SQL and exposing it through a thinner API, but rejected that option because it would preserve the existing coupling and make testing, observability, and future changes harder. The migration was done incrementally to avoid disrupting production behaviour.
Outcome: The workflow became easier to maintain, debug, and extend from the backend layer. Business logic was no longer concentrated in database procedures, production issues became easier to trace, and new integrations could be added without modifying the entire legacy flow.