The container diagram is a even further "zoomed-in" version of the Container Diagram and shows the software architecture within a single container. You dont have to create this diagram for every container, usually it is done for containers that need to be custom-coded. This most prominently includes the frontend and backend containers as well as special components, like a batch component or an complicated adapter. A bounded context might also be implemented as its own component, if it isn't big enough to justify its own container.
Example Component Diagram:
Adapted from https://c4model.com (CC BY 4.0). Changes made.
Example Template:
Design Principles
Modularity
Expanding on the ideas presented in Modular Design, a modular approach is also recommended within a container
Try to identify components and especially business components / domain components that encapsulate a specific area of concern
the data model is usually a good starting point informing you of areas of high cohesion
Some commonly used design patterns for dealing with external systems include Adapter, Proxy & Facade (see Software design pattern - Wikipedia).
Adapted from a CC0 1.0 public-domain diagram (Wikimedia Commons). Changes were made.
