To find bottlenecks and to help with debugging and monitoring
For deploying to a VPS like DigitalOcean. This pairs nicely with https://github.com/cyrusstoller/gardenbed.
If you want to run this for free on a single dyno, you can use heroku
Because I like having more control of my deployment, I am currently hosting this on DigitalOcean. I don't need to worry about arbitrary row limits and I can be sure that the app is always running.
To keep track of who is visiting the site.
To keep track of who is visiting the repo, but Github recently started offering something similar with https://github.com/cyrusstoller/RevTilt/graphs/traffic.
To make sure that I don't push bugs to production.
For sending emails. I use this primarily for password resets in this application.
To keep code and manage collaboration.