I support 100 < n < 150 servers for 6 hours of a chase-the-sun rotation. I'm personally responsible for around 40 servers, across 5 cloud locations, providing

I support 100 < n < 150 servers for 6 hours of a chase-the-sun rotation. I'm personally responsible for around 40 servers, across 5 cloud locations, providing a backend to ~5 products. These are all configured with the same software stack: a DB, an LDAP running on top of that, and a web service or two for interacting with the data. We have deployment, configuration and monitoring systems (avoiding naming specific products as it'd be easy to figure out my name, etc...) and avoid touching the live systems directly wherever possible. Chances are, if something needs to be done for one system, it needs to be done for all (can schedule individually), and it keeps things consistent. In case of failure, we know we can consistently redeploy our systems (assuming data backups are available).