An important caveat is that C4 is narrowly tailored to monolithic software systems. When diagramming cloud or (micro-)service systems, its prescribed abstractions start to work against you. For example, there is no appropriate level for (e.g.) VPCs, virtualized containers, or abstract concepts like microservices. At that point, you’re left either abandoning C4 or debating with everyone about the exceptions you have to make to make it fit.

> C4 approach to diagramming

This highlights my only beef with TFA, since it seems to go against the advice to not mix abstraction levels.

TFA is great advice for getting at least mediocre diagrams, informative and inoffensive. But the best diagrams are deliberately mixing levels to highlight stuff, because layer boundaries are usually where it gets tricky. Maybe none of this is relevant if you really want to split hairs about what architecture vs system vs component diagram “really” means, but I’m not aware of nonfuzzy definitions for that and most people seem to use the terms informally.

There is some interesting new working the C4 space at https://likec4.dev/

This is a less prescriptive model than structurizr but keeps the goals of C4