C4: Nested Boundaries Component
A C4 Component diagram with a boundary nested inside another boundary, plus components wired to a database outside both.
c4-nested-boundaries-component.mmd
C4Component
Container_Boundary(api, "API Application") {
Boundary(web, "Web Layer") {
Component(ctl, "Controller", "Express", "Routes requests")
}
Component(svc, "Service", "TypeScript", "Business rules")
}
ContainerDb(db, "Database", "Postgres")
Rel(ctl, svc, "Uses")
BiRel(svc, db, "Reads and writes", "SQL")