From a business perspective: You might not have to solve that problem at all in 6 months, because you might not get so many users for the product, that scalability is a problem. You often need velocity more than clean code, because you are not sure if the idea will get traction at all. In that case, from a business perspective, to be able to experiment you need velocity more than a good data model.

I did this kind of exploratory development both with SQLite and Postgres, both had different strengths and weaknesses. Had the purist clean data model with Postgres cost more than it should have when the product had to pivot the product. Also have seen the scalability limits of SQLite. Just shutting down a POC project backed by SQLite, which failed to get traction mostly because of business execution problems, and SQLite saved a lot of effort for the implementation, and using a "cleaner" and "more scalable" solution would have only reduced velocity, but would not have got us more users, the system worked fine this way (even has N+1 queries in some places). Should we got to the point that SQLite starts to become a bottleneck we could have afforded to clean the data layer (we had to rework countless times already as requirements were in a flux) up a bit and move to more scalable solution. Others might stick Firebase or MongoDB there, and it also does work for a while, and that is also a valid decision IMHO from a business perspective.

I think this is a kind of topic where the premature optimization is the root of all evil meme can apply, depending on the product you are making and the available resource pool. Not for the hello world examples of course, and not for the well defined well funded project, but there are lot of exploratory attempts out of the bigco/vc funded unicorn world.

But the thing is that in SQLite you effectively don't have N+1 issues.