At Replit, the company aims to ensure a high session success rate, with a goal of always successfully connecting legitimate incoming requests from clients to their target Repl. To achieve this, they introduced a new reverse WebSocket proxy called Eval, which abstracts away intermittent infrastructure failures by sitting between the client and Conman VMs. This separation of concerns addresses several issues in their previous architecture, including frequent Conman updates causing multiple disconnect events for clients, Conman's sole job being container hosting making autoscaling complicated, and diagnosing session failure rates being harder due to shared functionality. Eval provides a more reliable connection experience with fewer reverse proxy failures, easier observability, and scalability based on active client connections.