advancedReal System Design Problems
Design a Digital Wallet (like PayPal or Venmo) — atomic transfers and idempotent payments.
The financial consistency and idempotency problem: how transfers between accounts are made atomic, how the system prevents double-charging on a retried request, and how transaction history is stored for auditability. Idempotency keys on every payment operation are the central design detail interviewers probe hardest.
Ready to design this system end to end?
Generate a complete, structured system design answer — requirements, capacity estimation, API design, architecture, database choice, scaling, caching, fault tolerance, security, trade-offs, and more, walked through the way a strong senior engineer would in a real interview.
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