System Design · Affirm · Medium
Design a payment processing service for a user's existing installment loan. A payment can be started manually from a mobile app or website, or it can be generated automatically by a scheduler. The service must call a bank debit API that only accepts requests during one fixed one-hour window every day and returns a synchronous result while that window is open. After each attempt, the service must notify the user by SMS or email whether the attempt succeeded or failed. Your…
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