Agents or a proxy: the access-control decision you make before you compare any features

Disclosure: I work on Tessera, which is one of the proxy-shaped tools. Both shapes are legitimate and I try to be fair to the other one below. Most comparisons of access-control tools start with feature tables. That is the wrong end. The decision that actually determines whether a rollout finishes is the deployment shape, and there are only two. Shape one: agents and certificates You run an internal certificate authority. Hosts are configured to trust it. Users get certificates that expire in a few hours. For Kubernetes, an agent runs inside the cluster and brokers access from there. What this buys you is genuinely good. Expiry does revocation automatically, which removes the human step that fails. The credential on the user's laptop is worthless tomorrow. The model scales well because the CA does not sit in the data path — once the certificate is issued, the user talks to the target directly, so there is no proxy to size and no bandwidth to plan. What it costs is that you have to change production before you get anything. sshd_config gets rewritten across the estate to add TrustedUserCAKeys . An agent gets deployed into every cluster. In some setups the tool's binary is copied onto hosts. None of that is technically hard. It is organisationally hard. You need a change window, sign-off from whoever owns those hosts, and a rollback plan — for a project whose entire benefit is "nothing bad will happen later". That conversation is where access-control rollouts stall, and it stalls most reliably in exactly the organisations that need the tool most: the ones where nobody is quite sure who owns which box. The other cost is that the CA private key becomes the most sensitive object your company owns, and now you operate a CA. Shape two: a proxy The credential stays on a controller. The user authenticates to the controller. The controller opens its own connection to the target, authenticates with the real credential, and relays. The target sees a normal connection from a nor