Engineer Architecture flashcards

34 cards. Read the term and the definition here. The deck at the top of this page is optional.

Architecture

The set of structures (components, relationships, principles) and decisions that are hard to reverse and needed to reason about the system; excludes easily changed design detail.

Instability metric

I = Ce / (Ca + Ce), where Ce is efferent (outgoing) coupling and Ca is afferent (incoming) coupling. I=0 means maximally stable; stable packages should be abstract.

Dependency inversion principle

High-level policy depends on abstractions, not details; both depend on interfaces owned by the policy layer. Implemented as ports and adapters (hexagonal architecture).

Conway's Law

System structure mirrors the communication structure of the organization that builds it. The inverse Conway maneuver deliberately shapes teams to obtain the target architecture.

Quality attribute scenario

A six-part testable requirement: source, stimulus, artifact, environment, response, and response measure. Without a measure the requirement is not verifiable.

Stakeholder power/interest grid

Classifies stakeholders as key player, keep satisfied, keep informed, or monitor based on power and interest; each stakeholder's concerns become quality attributes.

Requirements traceability matrix

A table linking stakeholder needs to requirements, architecture elements, and test cases; supports impact analysis when a change is proposed.

MoSCoW prioritization

Ranks requirements as Must, Should, Could, or Won't. Scope is negotiable under MoSCoW, but the definition of done is not.

C4 model

Four zoom levels: Context, Container, Component, Code. Each layer answers a different stakeholder question; mixing abstraction levels in one diagram is an error.

ArchiMate layers

Business, Application, and Technology layers connected by serving, realization, and access relationships; used to express cross-layer traceability in enterprise architecture.

View and viewpoint

A viewpoint is a template derived from stakeholder concerns; a view is a representation conforming to it. ISO/IEC 42010 governs architecture descriptions.

Provided and required interface

A component contract has a provided interface (what it offers) and a required interface (what it consumes); modeling both exposes missing dependencies.

Availability formula

A = MTBF / (MTBF + MTTR). 99.9% availability allows about 8.77 hours downtime per year; 99.99% allows about 52.6 minutes.

STRIDE threat model

Six threat categories: Spoofing, Tampering, Repudiation, Information disclosure, Denial of service, Elevation of privilege; used to derive security requirements.

Scalability versus elasticity

Scalability is the design property to handle growth by scaling up or out; elasticity is the ability to scale automatically with changing demand.

Testability tactics

Design choices that ease testing: abstract interfaces, record/playback, sandboxing, and built-in self-test hooks; a system hard to test is hard to change.

REST constraints

Client-server, stateless, cacheable, uniform interface, layered system, and optional code-on-demand; HTTP methods should be idempotent where the specification defines them.

Saga pattern

A sequence of local transactions with compensating actions that maintains consistency across services without a distributed transaction; introduces eventual consistency.

Interoperability layers

Syntactic (format and protocol), semantic (shared meaning), and organizational (process and policy). Most integration failures are semantic rather than syntactic.

API versioning strategies

URI versioning, header versioning, and media-type versioning. Deprecation requires a documented sunset period; additive changes remain backward compatible.

Sensitivity point

An architectural decision that significantly affects one quality attribute; a tradeoff point affects two or more attributes in opposite directions.

Utility tree

ATAM artifact: quality attribute refined into scenarios, each rated for importance and difficulty of realization, used to prioritize evaluation effort.

Fitness function

An automated test that continuously verifies an architectural characteristic, such as dependency rules, performance budgets, or security checks, in the CI pipeline.

Risk versus non-risk

In ATAM, a risk is a decision with potentially undesirable consequences; a non-risk is a good decision. Risk themes aggregate related risks for management.

Architecture decision record

A document with title, status, context, decision, and consequences. Accepted ADRs are immutable and superseded by a new ADR rather than edited.

ISO/IEC/IEEE 42010

Standard for architecture description defining stakeholders, concerns, viewpoints, views, and correspondence rules; the basis for documenting architecture descriptions.

arc42 template

Documentation structure covering context, constraints, solution strategy, building blocks, runtime, deployment, decisions, and quality; sufficient rather than exhaustive.

Governance exception process

A documented route to deviate from a standard with rationale, approval, and expiry; exceptions are tracked as governance metrics.

Blue-green deployment

Two identical environments; traffic is switched from blue to green after the new version passes checks, enabling near-instant rollback.

Error budget

Error budget = 1 - SLO. Burn-rate alerts fire when the budget is consumed faster than planned, triggering reliability work.

Deployment versus release

Deployment puts code into production; release exposes it to users. Feature flags decouple the two and allow gradual rollout.

Expand-contract migration

Backward-compatible database change in three steps: add new schema, migrate and dual-write, then remove old schema after consumers move.

Ethical escalation duty

When asked to approve an architecture you believe unsafe, document the concern in writing and escalate; do not silently comply or sign off.

SBOM

Software bill of materials listing third-party components and licenses; supports license compliance (permissive versus copyleft) and vulnerability response.