Every Backend Engineer needs to know how to deal with payments.

Implementing a reliable payment retry system is crucial for handling payment failures like network issues or expired cards. Key elements include tracking payment statuses using an append-only database, utilizing retry queues for transient problems, and a dead letter queue for persistent issues. Distinguishing between retryable and non-retryable errors is essential to avoid unnecessary retries and customer frustration. Exactly-once processing guarantees prevent duplicate charges in retries.