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Tiller was a server-side (running on Kubernetes cluster) component of Helm. Its main purpose was to make possible for multiple different operators to work with the same set of releases. In Helm 3 the same information are fetched directly from the API Server. Charts are rendered client-side which makes Helm 3 more “native” and simpler. The security model for Helm has been simplified (with RBAC enabled locking down Tiller for use in a production scenario was quite difficult to manage).