Design
Online Auction System
Design an online auction platform like eBay supporting bidding, auto-bid increments, and auction closing.
This is a Low-Level Design (LLD) problem. New to LLD vs HLD? Start here.
01 - Why interviewers ask this
Live bidding under concurrency is a great test of atomic compare-and-set logic — interviewers watch for race conditions where two simultaneous bids could both "win".
02 - Where this system exists in the real world
You interact with this design every day.
eBay-style online auction platforms
Live charity and estate auction systems
B2B procurement reverse-auction platforms
03 - What you'll master
Solve this once. Know it forever.
Serialize concurrent bids safely
Implement proxy/automatic bidding logic
Design anti-sniping auction extension rules
04 - What you'll design
6 functional · 2 non-functional requirements.
List an item for auction with a starting price and end time
5 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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