Software Design

Flash Sale Waitlist & Cart Reservation

Use Case Diagrams · made in Skemio

Use case diagram for flash sale waitlist and cart reservation showing Shopper and Queue Worker interacting with queue and reservation flows.
Use case diagram for flash sale waitlist and cart reservation showing Shopper and Queue Worker interacting with queue and reservation flows.
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What it shows

  • Inventory holds use short TTL locks (e.g. 5 mins) before auto-expiring.
  • Virtual queues smooth write spikes by metering traffic to cart creation.
  • Waitlist notifications trigger asynchronously as reserved carts expire.

The takeaway

Seat-lock mechanisms decouple inventory checkout from queue admission to preserve database integrity.

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