System Design · Capital One · Hard
Design a highly reliable backend service for user account balances, such as a digital wallet or bank ledger. The service must expose these operations: Deposit funds into an account. Withdraw funds, rejecting the operation when the balance is too low. Transfer funds from one account to another atomically, so both sides apply or neither does. GetBalance(accountId) to read the current balance. Correctness is the top priority. The implementation must prevent lost updates, double…
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