every complex domain and “at scale” is just a bunch of simple things in disguise… our industry is just terrible in general about breaking things down. we sort of know this so we came up with shit things like “microservices” but you spend sufficient time in the industry (almost three decades for me) and you won’t find a single place that has microservices architecture than you haven’t wished was a monolith :) we are just terrible at this… there is no complex domain, it is just a good excuse we use to justify things