Senior Backend API Engineer

Senior Backend API Engineer (Contract) One day per week on-site in Brecksville, Ohio (4 days remote) About the Role We're building the API layer that lets AI assistants read staffing schedules and, with explicit human consent, reschedule work and create staffing requests. The API will serve two consumers: a large client's own AI agent platform today, and our in-app assistant down the road. The interesting problems here aren't UI polish. They're trust and correctness at the API boundary: Identity delegation: the assistant always acts as a specific end user, never with broad system privileges.Retry safety: assistants retry requests, and a retry must never double-book anyone.Human consent: every action requires a genuine human approval step that an AI model cannot fake. The architecture is already designed and documented. We're looking for someone senior to pressure-test that design, tell us where it breaks, and then help us build it. What You'll Build First delivery, the scheduling-conflict flow: surface scheduling conflicts, give the agent the context it needs to propose alternative slots, and commit a rescheduled assignment safely. Next, the request-intake flow: conversational creation of staffing requests through validated, metadata-driven dynamic forms, reusing the same identity, retry-safety, and consent foundation. This flow currently carries logic on the client side that needs to move server-side, so that the API and the user-facing application share one consistent source of truth. What We're Looking For Idempotent write design. You've shipped write APIs where duplicate or retried requests can't cause duplicate effects. Experience with banking, payments, or similar high-stakes write paths is ideal.API gateway policy work. The gateway will be hosted by the client, so you won't own it, but you understand how gateway policies work well enough to recommend the right setup to the client.Senior C# / .NET and SQL Server. You're comfortable with business logic living in the database. Our approach is to call existing stored procedures from the API, with the API responsible for shaping the data back into what the agent needs.