Figure out and set limits on usage

[cholmes]

We want to be sure that the service doesn't end up costing us lots of money, so we need to determine budget constraints and set the right limits in case something goes wrong (or right - we get way too much traffic and can't afford it).

[asmithml]

This task is going to remain open for a bit, but it is in progress. Right now we are limited by network I/O and the number of vCPUs. This will be updated as we make new changes and explore scaling options.