Prevent Duplicate Request Processing
Company: OpenAI
Role: Software Engineer
Category: System Design
Difficulty: hard
Interview Round: HR Screen
A client accidentally sends the same network request twice, for example because the user double-clicked a button, the client retried after a timeout, or the network duplicated a request.
Design a reliable way to prevent the operation from being processed twice. Explain both client-side and server-side mechanisms, and describe how your design handles concurrent duplicate requests.
Quick Answer: This System Design question evaluates understanding of idempotency, request deduplication, client- and server-side reliability mechanisms, and concurrency control in distributed systems.