Architecture Principles

Make boundaries follow business capabilities and rates of change.
Keep dependencies pointing toward stable policy, away from volatile details.
Hide decisions likely to change behind clear interfaces.
Prefer explicit data flow and ownership over invisible coupling.
Make invalid states difficult to represent.
Design operations to be observable, retryable, and safe under partial failure.
Delay distributed complexity until scale or organizational evidence requires it.

Architecture is the set of consequential decisions that are expensive to reverse. Record those decisions with Architecture Decision Record.