Senior Track

Handling Payments

Payments are one of the few places where a senior engineer's mistakes show up as real money lost. These lessons cover the patterns that production teams use to make payments safe under failure, retries, concurrency, and disputes. The framing is provider-agnostic; the examples use Stripe shapes because they're the most common.

1. Payment Intents vs Direct Charges 2. Idempotency Keys in Payment APIs 3. Webhooks: Verify, Idempotent, Replayable 4. Async Confirmation: Trust the Webhook 5. Refunds & Chargebacks as State 6. The Ledger Pattern (vs Balance Columns)

Want to drill these? The matching Practice cards turn each lesson into a scenario with discrete answers.

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