Requirements

• An auction is initiated by a seller and consists of a single product. It starts from 0$ and buyers can keep bidding(always at least current_winner + a predefined increment) until it expires.
• The seller can define a reserve price. Its presence is visible, but the actual amount is not. If defined and the final bid is less than the reserve price, the auction will fail with a separate status.
• Bidders might also make use of an autobidding system. Given a maximum value, each time the user is outbid, the system will automatically try to bid on behalf of the user with the smallest value possible(the predefined increment above will be used to reach this value; calculation must strictly follow it), up until the maximum value has been reached.
• The autobidding algorithm must be efficient time complexity wise.
• Once an auction completes, an external system will be notified of the result together with the winner(if any).