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Crypto / fintech
Coinbase interview themes
What people report studying for — not a take-home dump. Last editorial update 2026-08-14.
Ledger grainReconciliationIdempotency
Rounds you should expect
Ledger
Deposits, withdrawals, and fees as facts — not a running balance column you overwrite.
Ops
A webhook retried. How you do not mint two ledger rows.
Recently added questions
2026-08-28 · Ledger grain
A deposit webhook retried. How do you not mint two ledger rows?
Idempotency key (or natural key on payment_id + event_type) and an upsert. A running-balance column you overwrite is not a ledger.
From the question bank
hard · System design · System design
Payments ledger: webhook retries, partial refunds, and a warehouse. What is the grain of gold?
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