HotelTonight, an app for last-minute hotel booking, relies on Redis, an open source data structure server, to quickly sync reservations and vacancy information with a range of hotel reservation systems and users' devices. The app's Black Friday traffic peaked at eight times normal load levels, highlighting the need for real-time updates even under heavy load. Using Redis helps handle network timeouts and other errors in communication with customers' devices and third-party services like booking APIs. Additionally, it allows engineers to quickly add and tweak new features without building traditional database tables.