It's a risk either way.

But an equal risk? For most companies it isn't. Their are more failed big dreamers than companies that missed the big time because they couldn't scale.

It's a good question, and I don't know where the quantitative data exists to answer it.

My personal preference is to hire experienced teammates who have solved similar problems in the past, because at most levels of scale (other than, say, Google's or Facebook's), few problems are truly novel. So it's reasonably possible to predict where the business will be WRT technological requirements in, say, 1 to 3 years, sometimes 5 if you're just getting started, and plan accordingly.

In the case of this particular problem (time series data), there are some pretty easy and scalable answers out there -- Datadog, SignalFx, Wavefront, Prometheus, etc. to start with. So it's not like you have to waste a bunch of opportunity cost going out and building a solution.