[lmm]

If you understand the problem well enough to write a good domain model then you're basically already there - which is to say, you can only know you're modelling the right domain after you've found product/market fit. But to be able to find that out you need some level of product, which often means having working code before you fully understand what your product really is. At that stage, a schemaless database is very helpful; working out your domain model in detail and typing it out twice would be a waste of time when it's likely to change quickly.