Design
Peer-to-Peer Digital Wallet System
Design a P2P payment wallet supporting transfers between users, multiple funding sources, and transaction reconciliation.
01 - Why interviewers ask this
Peer-to-peer transfers are the fintech LLD staple for testing atomicity — interviewers specifically probe whether both sides of a transfer succeed or fail together, with no partial state.
02 - Where this system exists in the real world
You interact with this design every day.
Venmo / Cash App / PayPal P2P transfers
In-app peer payment features (ride-share tips, etc.)
Digital remittance platforms
03 - What you'll master
Solve this once. Know it forever.
Implement double-entry bookkeeping for transfers
Guarantee atomicity across two wallet updates
Design idempotent retries for payment requests
04 - What you'll design
6 functional · 3 non-functional requirements.
Link a bank account or card as a funding source
5 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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