Definition. A multi-instance TYPO3 setup in which several frontend pods or servers run in parallel behind a load balancer and share a common database, a common fileadmin and a distributed cache. Read load scales horizontally. Write operations (backend, indexing) typically run on dedicated instances.

Why it matters. Cluster operation is the answer to load peaks, rolling updates without downtime and high availability. At mid-sized companies it is usually the consequence of a concrete requirement (newsletter funnels, campaigns, AI crawlers), not an academic end in itself.

Related. TYPO3 Kubernetes, TYPO3, Kubernetes, Cluster Autoscaler