Keys do not scale, and they do not tell you anything

Ask an office of forty people who holds a key to the server room and you will usually get a confident answer and a wrong one. Keys are copied, lent, inherited from someone who left, and kept in a drawer that everyone knows about.

The problem is not that a key is insecure. It is that a key records nothing. When something goes missing, the lock cannot tell you who came through it, so the investigation starts from rumour.

Access control replaces both weaknesses at once. A credential is issued to a person, carries the rights that person needs, and can be revoked in seconds without touching the door. Every grant and every refusal is logged with a time, and if the door is covered by a camera the log and the footage line up.

The design decision that matters is scope. Rights should follow roles and schedules, not individuals. A contractor gets weekday daytime access to one zone. A night shift supervisor gets the doors that shift needs. Set up this way, a new starter is a role assignment rather than a set of decisions nobody records.

Doors still have to be safe. Every controlled door needs its fail-safe or fail-secure behaviour decided against the fire strategy, and emergency egress must never depend on a reader having power. That is a design question, settled on paper before hardware is chosen.

Done properly the result is quieter than people expect. Nobody carries a bunch of keys, leavers stop being a security event, and the question of who was where has an answer rather than an argument.