Solving Session Persistence for Model Context Protocol Servers at Enterprise Scale

Model Context Protocol (MCP) servers that work perfectly in development can fail intermittently once they are deployed across multiple replicas behind a load balancer. The failure mode is a stream of “session not found” errors that appear at random, and the cause is a mismatch between how certain MCP transports hold session state and how load balancers distribute requests. This article explains why the problem occurs, when it applies, and a concrete pattern for solving it using a shared session store.