ColdFusion Session Clustering with Redis: Setup, Failover, and Common Gotchas

ColdFusion’s native Redis session storage — available since ColdFusion 2016, with the redissessionstorage package on CF 2021+ — solves the fundamental horizontal-scaling problem: by default, ColdFusion sessions live in the server's memory and can't be shared across nodes, so a load balancer sending a user to a different node loses their session. With Redis as external session storage, every ColdFusion node reads and writes sessions to a shared Redis instance, so any node can serve any request. The setup is done in the ColdFusion Administrator → Server Settings → Memory Variables, by selecting Redis, providing the host, port, and password, and then unchecking "Use J2EE Session Variables" (mandatory — J2EE sessions and Redis session storage are mutually exclusive) and disabling sticky sessions at the load balancer. On CF 2021+ with the ZIP installer, first install the redissessionstorage package via Package Manager. The critical constraints to know up front: Redis Cluster is not supported — only standalone Redis; sessions are written back to Redis at the end of the request (not instantly during it); and in a cluster cflock no longer provides distributed session safety across nodes. This guide covers the complete setup, failover design, and the gotchas that cause production pain.
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