Software Design

Online Auctions: Bids, Sniping, and Reserves

UML Class Diagrams · made in Skemio

UML class diagram displaying AuctionListing, Bid, Bidder, and Settlement entities with relationships showing bidding increments and auction settlement.
UML class diagram displaying AuctionListing, Bid, Bidder, and Settlement entities with relationships showing bidding increments and auction settlement.
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What it shows

  • AuctionListing maintains state transitions, reserve price, and end timestamps.
  • Anti-sniping extensions mutate the auction deadline dynamically upon late bids.
  • Bid placement requires strict optimistic locking and increment validation.

The takeaway

Model bidding as an append-only event stream tied to a listing with dynamic anti-sniping timers.

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