Interview Q&A / System Design
System Design interview questions
Caching, scaling, databases and classic design problems for beginners.
Prefer rapid revision? Practise System Design short interview answers →
- How does an idempotency key stop duplicate payments?
The client sends a unique key with each payment request. The server stores the key with the result; if the same key arrives again, it returns the saved result instead of charging again.
IntermediateQuick answer1 min read