There is no single physical access control system that is the most flexible and scalable. That said, some systems are more flexible and scalable than others. For example, a system that relies on physical keys may be less flexible and scalable than a system that relies on RFID cards or biometric scanning.
That said, there are a few factors to consider when choosing a physical access control system. First, you need to consider the size of your organization and how many people will need access to the premises. You also need to consider the type of security you need. For example, do you need access only during certain hours of the day? Do you need access only for certain employees? Finally, you need to consider your budget. If you are looking for a budget-friendly solution, get in touch.