Translate security goals into architectural boundaries.
Apply secure defaults, isolation, and fail-safe behavior.
Evaluate trade-offs and blast radius.
Security architecture makes flows, privileges, dependencies, and failure behavior explicit. Layer controls around critical operations: identity, authorization, validation, protected persistence, telemetry, and recovery. Do not mistake a pattern name for evidence; test whether assumptions hold in your environment.
edge -> identity -> policy -> service boundary -> scoped data access
|-> audit -> detection -> response
Use isolation to limit compromise, secure defaults to reduce accidental exposure, and fail-safe behavior for sensitive decisions. Resilience must not become fail-open access. Record architecture decisions, alternatives, constraints, and residual risks.
Exercises
Draw secure boundaries for a payroll service.
Identify fail-open behavior in three scenarios.
Write an architecture decision record.
Self-check
What is blast radius?
Why document assumptions?
What is secure by default?
Self-Check Quiz
1. What does isolation reduce?
AnswerThe resources and services reachable after a component or identity is compromised.
2. Should a failed authorization check allow access?
AnswerNo. Sensitive authorization should fail closed and generate useful operational evidence.
Homework
Review a three-tier enterprise architecture.
Propose layered controls and failure behavior.
State cost, usability, and residual-risk trade-offs.
Sample answerUse identity-aware access, explicit service authorization, segmented data paths, scoped database roles, protected secrets, audit logs, detection, and tested recovery. A decision record explains complexity and what remains possible if an endpoint or identity is compromised.