How to build an auction system in Bubble

The core of an auction system in Bubble is simple: you store Auctions in the database, store Bids linked to those Auctions, and use backend workflows to validate and save bids so users cannot cheat by modifying values in the browser. Every time a user places a bid, you run a backend workflow that checks if the bid is higher than the current highest bid; if yes, it saves it and updates the Auction’s current price. The Auction also needs an end time, and another backend workflow that marks it as finished when time runs out.

Data Structure

• Auction: fields: title (text), end_time (date), current_price (number), status (text, e.g. “open”), highest\_bid (Bid).
• Bid: fields: amount (number), bidder (User), auction (Auction).

Placing a Bid

You never save a bid directly from the page. You trigger a backend workflow via “Schedule API workflow”. This prevents users from faking values using the browser.

• Create an API workflow like “place_bid”. Parameters: auction_id (text), amount (number).
• Inside the workflow: find the Auction using “Do a search for Auction:first item where unique id = auction\_id”.
• Check conditions: only continue if auction’s status is “open” AND amount > auction’s current\_price.
• If valid, create Bid → set highest_bid for Auction → update current_price.

// In the button "Place Bid" workflow (frontend)
Schedule API workflow: place_bid  
auction_id = Current Auction's unique id  
amount = Input Bid's value  

Ending Auctions

Use a backend workflow triggered at the auction’s end\_time.

• When creating an Auction, schedule an API workflow “close_auction” with date = end_time.
• Workflow checks if highest\_bid exists; sets status = “closed”.

Privacy Rules

• Users should never be able to modify Auctions or Bids from the browser.
• Allow “Create” for Bids only via backend workflow (unchecked for client). Same for Auctions.

Real-Time Updates

Set the page or group containing the current price to “Do every 5 seconds” → “Display data” from database so users see fresh prices.