I just ran across a pretty good series of posts on modular monoliths:
Modular Monolith: A Primer - Kamil GrzybekWhat is a Modular Monolith
architecture - introductory post in article series about monolithic and modular
systemsKamil GrzybekKamil Grzybek
[http://www.kamilgrzybek.com/design/modular-monolith-primer/]The first article
in the series