Online Auction Web App with Live Bidding and Countdown Timers

An online auction web app with live bidding and countdown timers lets buyers compete for items in real time: each lot carries its own ticking clock, bids arrive instantly, and the highest bid when the timer hits zero wins. Classroom auction projects usually fake this with page refreshes or static timers, so students never learn the genuinely hard parts — pushing bid events to every connected browser, validating concurrent bids against a moving price, and closing auctions fairly when the clock runs out. This project implements the real thing: a WebSocket-powered bidding engine that broadcasts every valid bid to all viewers at once, per-lot countdown timers driven by server time, minimum-increment bid validation, public bid histories, a watchlist, and seller listing creation. An anti-sniping rule extends any auction that receives a bid in its final 90 seconds, closing the classic last-second-snipe loophole. The shipped build is a complete teaching-grade marketplace with source code, database schema, deployment guide and the full viva kit.

1. A seller creates a listing with title, category, condition, starting price and duration; the lot appears on the live grid with its countdown running.
2. The frontend renders each lot's timer from the server-provided end time, ticking down every second; the server's clock is the authority for closing.
3. A buyer opens a lot and places a bid; the backend validates it against the current price plus the minimum-increment rule for its price band.
4. Valid bids are written to the database and broadcast to every connected client over WebSockets, updating price, bid history and bid count everywhere at once.
5. If a bid lands in the final 90 seconds, the server extends the lot's end time by 90 seconds and broadcasts the new close time to all viewers.
6. When the timer reaches zero the auction closes; the highest bidder is marked the winner, the lot shows "Sold", and the full bid history is retained as the record.

Tech stack:

• Node.js · Express
• MongoDB
• Socket.IO
• React
• JWT authentication
• HTML · CSS · JavaScript
• Nginx (deployment)
• Git

• [Live auction lot grid] The home view shows every open lot with its live countdown, current bid and bid count, refreshing every second; category filters and search narrow the grid. (Implemented)
• [Place-bid flow with validation] The bid box enforces the minimum increment above the current bid, with quick-bid buttons at +1, +2 and +4 increments; invalid bids are rejected with a clear message. (Implemented)
• [Per-lot public bid history] Every bid, bidder and timestamp is listed on the lot page, newest first, so the full bidding trail is transparent to everyone. (Implemented)
• [Countdown timers with anti-sniping] Each lot carries its own ticking timer driven by server time; a bid in the final 90 seconds extends the auction by 90 seconds, defeating last-second sniping. (Implemented, extension length configurable)
• [Watchlist] Users can track lots with one tap; the watchlist tab keeps followed lots one click away with their live timers. (Implemented)
• [Seller listing creation] A create-listing form (title, category, condition, starting price, duration, description) publishes a new lot to the grid instantly, with a "My listings" panel showing status and bid counts. (Implemented)
• [WebSocket live-bidding engine] The shipped build pushes every valid bid to all connected browsers over WebSockets — price, history and timers update everywhere with no refresh. The single-file demo simulates rival bids with clearly labeled bots to demonstrate this behavior. (Implemented in the shipped build; simulated in the demo)
• Optional / future scope: payment-gateway integration (Razorpay/Stripe class) is NOT part of the base build — settlement happens buyer-to-seller; proxy/max-bid auto-bidding, reserve prices, admin moderation panel and a mobile app are future scope.

• Complete source code (Node.js/Express backend, React frontend)
• MongoDB schema with seed data for demonstration lots
• WebSocket live-bidding engine with anti-sniping logic
• JWT authentication for buyers and sellers
• Setup and deployment guide (local + Nginx)
• Project report PDF (background, architecture, methodology, results)
• PPT presentation for final review
• Viva Q&A preparation document (WebSockets, concurrency, validation, timers)