# Build an Auction Platform in Lovable - Tool: Lovable Prompts - Last updated: June 2026 ## TL;DR Paste the starter prompt below into Lovable Build mode and get a timed-auction marketplace scaffold with live bid feeds, a server-side bid validation RPC using SELECT FOR UPDATE to prevent lost-update bugs, and a Stripe charge-on-close flow. Full build takes a few days and around 200-350 credits on a Pro plan with top-ups. ## Frequently asked questions ### Can I run this on the Free Lovable plan? You can start on Free for the first few prompts, but the full auction build will exceed the 30-credit monthly cap quickly. The place_bid RPC alone takes 40+ credits to get right, and Stripe wiring adds another 60-80. Plan on Pro $25/mo from the start and budget 1-2 top-ups. The Free plan's 200 concurrent Realtime connections cap is fine for a soft launch. ### Why can't I just insert into the bids table directly from React? Two reasons. First, two browser tabs can send bid requests simultaneously, and without a SELECT FOR UPDATE lock inside a database transaction, both writes can succeed — meaning two bidders both get a receipt claiming they won with the same amount. That is a real money dispute. Second, a determined user can open DevTools, call the Supabase JS client directly, and send any amount they want — bypassing your React validation entirely. The place_bid RPC running inside Postgres with server-enforced rules is the only correct pattern. ### What happens if the Stripe charge fails after the auction closes? The charge-winner function sets payments.status to 'failed' and sends the winner a payment-link email so they can complete the purchase manually via a hosted Stripe checkout. In /account → Won Items, the winner sees a 'Complete payment' button. If they don't pay within 48 hours, you can cancel the sale and relist — add an admin action in /admin/moderation for this. Do not attempt automatic retries for charge failures; Stripe's built-in retry logic handles declined cards on subscriptions but not one-time PaymentIntents. ### How do I handle bidder cancellation or non-payment? There is no automatic non-payment resolution in v1. You need an admin workflow: in /admin/moderation, add a 'Cancel sale + relist' action on any auction in the closed state with a pending payment. This resets the auction status to 'draft' and lets the seller edit and relist. For repeat non-payers, add a blocked_bidders table and check it in place_bid — the anti-shilling follow-up prompt is the right place to add this. ### Can I run multiple auctions simultaneously without overwhelming the Realtime tier? Yes, but watch the connection count. Each auction detail page open by a user consumes 2 Realtime connections (one for the auctions channel, one for the bids channel). The Free Supabase tier allows 200 concurrent connections total across all auctions. If you run 10 simultaneous auctions with 10 viewers each, that's 200 connections — at the cap. Upgrade to Supabase Pro ($25/mo) for 500 connections when your auction volume grows. The 30-second polling fallback in the Realtime follow-up prompt acts as a safety net for spectators who can't get a connection. ### Is this legal — do I need an auctioneer license? Auctioneer licensing requirements vary significantly by jurisdiction. In the United States, most states require a license for live or online auctions of certain goods, especially real property, art, and livestock. Running a closed B2B surplus or charity auction for your own inventory is generally lower-risk. This page builds the software, not legal advice — consult an attorney familiar with auction law in your jurisdiction before opening to the public, especially if you plan to handle high-value goods or take a percentage of sales. ### Can RapidDev build a production auction platform for me? If your build outgrows this prompt kit and you need custom architecture, RapidDev builds production-grade Lovable apps at $13K-$25K — book a free 30-minute consultation at rapidevelopers.com. --- Source: https://www.rapidevelopers.com/lovable-prompts/lovable-prompts-for-building-auction-platform © RapidDev — https://www.rapidevelopers.com/lovable-prompts/lovable-prompts-for-building-auction-platform