This is true for typical Web loads. Companies with fewer users could have scaling problems earlier if their load is very write-heavy, if they generate artifici

This is true for typical Web loads. Companies with fewer users could have scaling problems earlier if their load is very write-heavy, if they generate artificial load from things such as crawling, if they have stricter latency requirements... Moreover, note that Redis server. Stack Exchange uses caching very agressively [1], it is not the relational database doing all the work. All that being said, I don't disagree in general: most startups should stop worrying about how they will scale their DB and stick with simple solutions that work. [1] http://meta.stackexchange.com/a/69172 http://meta.stackexchange.com/a/69172