There's a (sort of) objective trade-off to be made, but another dimension is how familiar you are with the solution and/or how quick can you implement it using documentation and examples.
If you happen to know exactly how to create a horizontally scalable microservice based hairball with nodejs, then maybe you are quicker with that than with some traditional django monolith using a nicely normalized sql database (or whatever).
In a startup, you are often always squeezed for time, so making the objectively right tradeoff for your context is usually secondary to the simple question of 'when can you ship?' If the scalable-yet-inflexible is what stack overflow abundantly recommends and documents, maybe this is quicker to get done now, whatever the consequences are on the longer run.