I lean towards amazon because I know that my usage should be low. I made a web app that is useful for my school, but it is not a revenue-generating site. I'm

I lean towards amazon because I know that my usage should be low. I made a web app that is useful for my school, but it is not a revenue-generating site. I'm willing to pay for low-usage hosting, or have my school pay for hosting. But neither I nor my school would be willing to pay for spikes in usage. I think there's a pretty small chance of such a spike, but I want to better understand how to control for that before setting up hosting on a per-usage model such as amazon.