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Code RoomMulti-currency ledger
HardPrep Room Coding #3245

Multi-currency ledger

System designDistributed systemsSenior–Staff~50 min

Design a multi-currency ledger for a cross-border money app where a user holds balances in 30+ currencies and can convert between them at a quoted rate. ~6,000 conversions/sec. Each conversion debits one currency balance and credits another at a locked FX rate, and the company books a spread as revenue. Describe the data model, how you avoid rounding/precision errors that leak or create money, and how you keep per-currency balances correct and reconcilable.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts (data model, bottlenecks, consistency, failure modes) and name the trade-offs you are making.

Clarify5:30 left
Estimate5:30 planned
Design16:30 planned
Deep dive13:30 planned
Failure9:00 planned
0:00
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