I had a tiny business web site running a few 100 maybe 1000 http requests per minute, either static or doing minimal php/mysql work. So I hired a cloud machine

I had a tiny business web site running a few 100 maybe 1000 http requests per minute, either static or doing minimal php/mysql work. So I hired a cloud machine of 512MB because shoestring budget. Resized a few memory pools. It worked great, until the mysql dataset grew enough. There was a backup job running 7z and pulling the compressed DB to a storage machine. It turns out 7z crashed because of the OOM killer. The http service itself just kept going on, OOM or not. Presumably because backup ran at 3AM and almost nobody was using it at that time.