Need Suggestions for SFTP Setup on EC2 with High Availability

Hello,

I currently have an SFTP setup on an EC2 server where client users are created locally. There are over 200 clients, and this number is expected to grow in the future. The issue is that whenever server maintenance is required, it impacts all clients, and if the server experiences an error, we have been recovering using daily backups.

I need to re-architect the setup to eliminate the single point of failure. The plan is to autoscale the server for both high availability and maintenance without affecting clients during downtime. The challenge I'm facing is how to replicate client user data across multiple EC2 instances.

I'm not confident in using a central Active Directory or a network database for this solution. My current thought is to use a common file storage solution like EFS or NFS to store client local files (e.g., /etc/shadow, /etc/passwd, etc.) and connect all EC2 instances to it. However, this approach feels risky.

What would be the best solution for scaling this setup in the coming days as the client base grows?

Thanks in advance for your suggestions!