How to be a responsible single founder?
imp: I use Binary Canary to alert me for down-time, which is about the same thing that Pingdom does.Just do whatever it takes for you to fall asleep at night.  I recently bought a smartphone (N900) that allows me to ssh into my server from anywhere, so if a small fix is needed, I can do that quickly.  Before I had that, I actually took my laptop camping with me during a busy period last year and drove to a nearby coffee shop periodically to check for any important issues.Other than that, I'd say to scale up your architecture as your site gets more popular.  If you later need some dual-DB setup with a heartbeat monitoring system then you can add that when the time comes.Have good backups too.  That might be more important than just uptime.