R3Stack is a software company founded by three engineer brothers in Brno, building AI-powered Shopify apps for merchants. Its products are designed to help online stores prevent overselling, protect product launches from bots, and improve the shopping experience. Its featured app, Cart Reserve, manages Shopify inventory reservations from the moment a shopper adds an item to their cart through checkout.

Merchants can choose reservation modes, set rules for individual products, and automatically return stock when a hold expires. Shoppers can see how long their items are reserved, while competing customers are informed promptly when inventory is no longer available. Cart Reserve also screens reservation requests for suspected bots, supports IP and country blocking, and applies per-IP hold limits.

A live dashboard provides session, conversion, expiry, and security information, with session-level details for holds and blocks. The app includes a fail-safe checkout rule intended to let genuine customers continue checkout if the app or its scoring service is unavailable