There aren't any as long as you don't use too much CPU or RAM (usually that happens when you have poorly written PHP that hogs RAM or gets stuck in a loop, or complex SQL queries that take a long time to evaluate). The servers have unlimited bandwidth. As long as your code is well-written and not a CPU or RAM hog, you should be fine. I moved almost half a terabyte of data last month on Tommy (in my case file downloads). If you do end up suspended for load, it's not the end of the world. Just let us know and we can help you figure out what's causing it and how to fix it.