Ask HN: Where do you draw the line of over-engineering?

Hello everyone, I am starting something new from July and was doing homework as usual to figure out what stack I would start out with.

I am going to build a marketplace for shipment of things. Demand/supply discovery/matching (lots of variables) plays a big role. We want to make it really cheap for very small businesses to use us.

The obvious question that came to mind: should I use technologies that I know? That would be Python/PostgreSQL/React/Redux/RESTful. On the other hand introducing GraphQL seems logical to me, but it is outside the comfort-zone of REST. Or say using non-Python stack for demand/supply messaging.

So even small changes might seem over-engineering if I have a learn about them, but in the long run they might be well suited to the problem. If I was experienced in something else (Golang/Elixir/GraphQL...) I would pick that for my stack. So personal preference plays a huge role in what we call "over-engineering". Where do you draw the line?

Thanks for your thoughts