I hope this solution is scalable because we already implemented this system for more than one client.

We have about 10,000 users. They are in many departments: accounting, business, IT, etc. 

We have three people that maintain the system because the first implementation is already online, so the troubleshooting goes to the administration. The daily work is managed in two versions. The first one has many changes. The other is fine to handle day by day, with actions such as add user, remove user, etc.

In terms of scalability, we have not seen any issues. The scalability is very good.

I have done deployments for five hundred users, five thousand users, and even ten thousand users.

The scalability is a bit of a concern based on my discussions with IT. 

We have around 200 users using this solution. We require three staff members for the maintenance of this solution. We do have plans to potentially increase the usage.