Abstract: A online marketplace that can connect nearby buyers and sellers in a time-sensitive and efficient manner. The system can enable users who want something to connect with nearby users who can provide that something by utilizing automatically detected location data from the users' computing devices. The system can allow both buyers and sellers to post listings, and can also allow listings to define multiple quantities of an item or service and allow multiple offers to be made and accepted on such listings via an auction mechanism. The system can improve the efficiency with which buyers and sellers can quickly find each other by not allowing users to submit offers on listings with price changes that degrade the listing. The system can also improve the efficiency with which buyers and sellers complete their transaction by facilitating a peer-to-peer payment process with dispute resolution controls.