Amazon Prime Day: a cart that never says no, an order that happens once

How a cart, checkout and order pipeline survive the busiest days of the year: Prime Day 2026 peaked at 192 million DynamoDB requests a second across all of Amazon's systems, but the service itself sees about 5,000 orders and 100,000 cart operations a second (assumed). A cart that never refuses an add, built from tagged lines and tombstones so removes stay removed where the 2007 Dynamo cart let them resurface; one purchase id per checkout page, recorded with the order and an outbox row in one transaction, so a retry returns the same order and a changed cart is a mismatch; retries at one layer; a hot deal split into sub-counters that sum to its stock; customer cells and shuffle-sharded shared services that keep a bad deploy to one cell in forty; and an orchestrated order pipeline where a payment timeout is unknown, not failed, and backlogs drain fresh work first.