Design an Idempotent Ledger Service | Stripe System Design Interview

What happens when a ledger commits a transfer, the response disappears, and the client retries? This tutorial designs an append-only, balanced ledger whose posting API returns one durable outcome across duplicate requests, races, crashes, and lost responses. We cover scoped idempotency keys, canonical request fingerprints, atomic ledger commits, outbox-driven projections, hot-account contention, watermarked reads, reconciliation, and linked reversals. Practice the complete problem on FastPrep: https://www.fastprep.io/system-design... This is an illustrative interview exercise, not a description of Stripe's production architecture. #SystemDesign #SoftwareEngineering #TechInterview #DistributedSystems #Stripe