Ask HN: how to estimate users per server

[Sean_Hayes]

I know this is highly dependent on a lot of factors, but is there any rough estimate for how many servers you need for x amount of users? I'm trying to estimate my future costs.

I'm using an Nginx front end server, Apache with mod_wsgi for serving my Django app, and PostgreSQL. It's all hosted on Rackspace Cloud using the latest Ubuntu.

[swombat]

In order to get a useful answer, you're going to have to provide a better idea of what kind of app you're talking about.

To use a couple of extreme examples, if your app provides key-cracking services, and each user wants to crack 1 key per day, and each key takes about a server-day to crack, you'll need (duh) at least 1 server per user.

On the other hand, if your app is basically a blog, a single (beefy) server should be able to quite easily serve millions of readers a month with the right caching in place.