"I'll never need to scale so why bother? We aren't Twitter or Facebook or Google after all." This is the most common email I get, a question in the form of a thinly disguised rationalization for not having to worry about scaling. And in these days of giant transformer-like machines they are probably right. But what if there are Barry Bonds enhancing type forces at work that argue for the chances of your needing to scale being higher than you think?

And if that happens, how will you cross the scalability chasm? Will you want to completely change your architecture or evolve it from a tool-chain that was meant to scale from the start? Architecturally, that's the question you have to answer. Today's tool-chains are making it possible to grow a system from small to large without needing to implement complete architectural phase changes at various scale inflection points, but that's a different topic. We're trying to think about why you may actually need to scale, that is the question.

Tumblr is a good example of a product that grew beyond expectation because they managed both to execute and harness powerful growth factors. Tumblr is a "light" blogging service that probably didn't think they were Twitter or Facebook or Google either, but need to scale they did. From Tumblr: