Horizontal Scaling ColdFusion Applications: Load Balancers, Shared State, and File Systems

Horizontally scaling ColdFusion means running multiple ColdFusion instances behind a load balancer so traffic is distributed, performance scales, and one node failing doesn’t take the site down. But adding servers is the easy part — the real work is removing every assumption your application makes about running on one machine. Three things must be externalized: session state (in-memory sessions aren’t shared across nodes — move them to Redis via ColdFusion’s native external session storage), the file system (a file uploaded to Node 1 doesn’t exist on Node 2 — move uploads to S3/Azure Blob or shared storage), and application-scope caches and locks (per-node application scope and cflock don't span nodes — use a distributed cache). One important, often-misunderstood point: ColdFusion's Cluster Manager in the Administrator does not do load balancing — it primarily enables in-memory session replication (which Adobe itself doesn't recommend). Actual load balancing happens at the web-server connector or a dedicated load balancer. Also note CF clustering requires Enterprise, Trial, or Developer edition — it's not in Standard. This guide covers the full stateless architecture with verified ColdFusion specifics.
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