C4

The C4 model is a lean graphical notation technique for modeling the architecture of software systems.[1][2] It is based on a structural decomposition (a hierarchical tree structure) of a system into containers and components and relies on existing modelling techniques such as Unified Modeling Language (UML) or entity–relationship diagrams (ERDs) for the more detailed decomposition of the architectural building blocks. https://en.wikipedia.org/wiki/C4_model software architecture diagrams

https://c4model.com/

Defines 4 levels of details. You can start with a broad/complete Level-1 diagram, then do to deeper levels for the parts that warrant it.