Building Waiting Room on Workers and Durable Objects

Cloudflare is expanding the availability of its Waiting Room feature, which helps manage high traffic volumes on web applications by creating an orderly queue during demand surges. The system was initially built for COVID-19 vaccination web applications and is now being made available to customers on Business and Enterprise plans. The main job of the Waiting Room is to protect a customer's application while providing a good user experience, ensuring that the number of users does not exceed limits set by the customer without degrading performance for end-users. The feature works by issuing tickets in the form of encrypted cookies to users and automatically creating an orderly queue during traffic spikes. It is designed to be highly scalable and resilient, using Cloudflare Workers and Durable Objects to handle coordination between data centers.