Engineering a Real-Time Reverse Auction Engine for the UK Used Car Market
How I built a timed reverse auction engine for Everyday Car Auctions — handling concurrent bidding without race conditions, dual-mode selling (auction + instant offer), and vehicle listing syndication to AutoTrader and MOTORS.
Role
Full-Stack & Backend Engineer
Client
Everyday Car Auctions LTD (UK)
Timeline
Jun 2025 – Present
UK used cars
Market
Timed reverse
Auction model
Concurrent, race-free
Bid handling
AutoTrader + MOTORS
External platforms
About the Product
Everyday Car Auctions (ECA) is a UK-based digital car auction platform operating on a timed reverse auction model — vehicle prices drop at set intervals while buyers place competing bids, with the highest qualifying bid winning the sale. Sellers can list via auction or receive instant offers. ECA also advertises vehicles on AutoTrader and MOTORS and is a proud match day sponsor of Stevenage Borough FC.
The Challenge
Building a real-time auction engine is one of the harder engineering problems in marketplace software — prices must drop on precise schedules, bids must be validated and ranked instantly, and the system must handle concurrent bidders without race conditions or lost bids. The platform also needed dual-mode selling, seller fee calculation, vehicle condition verification workflows, and integrations with external listing platforms.
What I Built
- Designed and built the core timed reverse auction engine — price drop scheduling, bid validation, and winner determination logic
- Built seller-facing workflows for both auction listings and instant offer requests with condition verification steps
- Developed buyer-facing bidding flows with real-time price updates and instant buy functionality
- Architected the backend API to support concurrent bidding without race conditions using database-level locking strategies
- Set up vehicle listing syndication to external platforms (AutoTrader, MOTORS)
- Built admin tooling for auction management, seller fee calculation (~8–9% + VAT), and bid oversight
Outcome & Impact
Currently in active development — building the complete auction platform from the ground up, delivering a production-ready system for the UK used car market.
Tech Stack
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