I work with a start up which currently doesn't have "big data", but perhaps "medium data". And, I can perhaps manage without a big data stack in production. But, if I look at the company/sales targets then in the next 6-12 months we will be working with clients that assures "big data".
Now, here are my choices - 1. Stick to python scripts and/or large aws instances because it works for now. If the sales team closes deals in the next few months after working tirelessly for months, then though the sales team sold the client a great solution, but in reality we can't scale and we fail. 2. Plan for your start up to succeed, plan according to the company targets. Try and strike a balance for your production stack that isn't an huge overkill now but isn't under planned/worked either.
It's easy to say we shouldn't use big data stack till we have big data, but its too late (specially for a startup) to start building a big data stack after you have big data.