Why do we organize by shape, and not by function in our monoliths? We put all our controllers in a package, all our DB accessors in another package, all our "data objects" in another package. Even in OO languages like Java where we have package accessors that never get used because we layout our code such that package scope can never be used. We instead layout the code according to "shape".

When figuring out what to spin-off as a microservice, we do this by functionality. Why not just make it easier in the monolith and organize by functionality instead? Let's act like 4yr olds, not 3yr olds: https://pubmed.ncbi.nlm.nih.gov/12090481/