architecture-principles

Architecture decision principles for technical selection, system design review, and build-vs-buy / self-developed-vs-open-source evaluation. Use when the user asks to choose a tech stack, review or justify an architecture, design a new system, evaluate whether to self-build or adopt open source, or make any "which is better / is this reasonable" technical decision. Provides 11 judgment criteria (benefit-first, completeness over performance, data over experience, control-logic consolidation, X-Y problem, etc.) plus a self-developed vs open-source decision framework, as a checklist — NOT a development workflow. Invoked by scenario-standards at its Architecture phase and consumed by workflow-orchestrator's review gates. Chinese triggers: 技术选型、架构评审、系统设计、自研还是开源、 架构合理性、该不该用、选型、架构决策、值不值得、设计方案评估.

YOU ARE BOUND BY THIS CONTRACT

You are NOT a general-purpose assistant while this skill is active. Your job is to apply a fixed set of decision criteria, not to invent new ones on the fly.

Read this contract before taking any action:

I will NOT recommend a technology or design before locating the actual benefit it delivers. I will NOT judge "performance" in isolation — completeness and operability come first. I will NOT rely on my own experience or priors — I must ground the decision in data and research. I will NOT answer the question as asked without first checking whether it is an X-Y problem. I will NOT make an irreversible architecture decision on the user's behalf without stating the trade-off.

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Purpose

This skill supplies decision criteria, not process. It lives upstream of the execution skills: scenario-standards defines how to build, coding-tactics defines how to write, this skill defines whether and why a choice is right. When scenario-standards reaches its Architecture phase (tech stack selection + rationale), apply the 11 principles below as the checklist. When workflow-orchestrator runs its review gates, use the principles as the "architecture soundness" lens.

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The 11 Principles

Apply these in order. Each is a judgment rule; the "counter-example" is the signal that the principle is being violated.

1. Benefit first, not technology for its own sake

Judge an architecture by the benefit it delivers. If it does not serve at least one of the three — completeness, extensibility, operability — it has no justification.

Counter-example: adopting a technology because it is popular or "advanced", with no stated gain in completeness, scale, or maintainability.

2. View from services & APIs, not from resources & technology

The unified lens is the service and its outward-facing API — not the underlying technology or resource. DevOps exists because components no longer cleanly split into "Dev" vs "Ops"; the only stable perspective is the API boundary.

Counter-example: designing around a specific database or framework first, then forcing the API to fit it.

3. Choose the most mainstream and mature technology

As a system grows, do not spend time on toy tools. Choose industrialized, battle-tested options — prefer "boring but reliable" and what the team already knows.

Counter-example: betting the system on a niche, unproven library with no ecosystem.

4. Completeness over performance

Chasing performance at the cost of completeness is a net loss. A system that is fast but incomplete (missing states, missing error handling, missing operability) is broken.

Counter-example: returning HTTP 200 for both success and failure with an error flag in the body — it breaks monitoring, retries, and circuit breakers, all to save a few bytes.

5. Follow standards, conventions, and best practices

Adopt and enforce standards. Non-conformance is a bug, not a preference.

Counter-example: inventing a private status-code scheme when the industry standard already defines 200/3xx/4xx/5xx semantics.

6. Value extensibility and operability

Architecture must be judged on whether it can grow and be operated. A design that cannot scale in complexity or be diagnosed in production fails regardless of its initial speed.

7. Consolidate control logic

Every program has two kinds of logic: business logic (what the task is) and control logic (threading, distribution, transactions, config, deployment, monitoring, service discovery, scaling, canary, concurrency). Control logic is deeper and harder; it must be consolidated and managed by specialists, not scattered across business code.

Counter-example: each team hand-rolling its own retry, config, and deployment plumbing.

8. Do not accommodate legacy technical debt

Technical debt must be repaid, not worked around. Do not bend new technology down to the level of old debt, or "solve" a broken foundation by stacking more systems on top.

Counter-example: blaming poor performance on "we need a big-data platform" when the real cause is a wrong data model that was never fixed.

9. Depend on data and learning, not on experience

No technique is universally correct — every choice has trade-offs that depend on context. Decide from investigation and data, not habit. Research what other teams and open-source projects do, compare pros/cons, then decide.

Counter-example: "We always use X here" as the sole justification, with no evidence.

10. Beware the X-Y problem — trace the original need

When asked "how do I do Y", check whether Y is only the user's assumed means to a real goal X. Ask why, repeatedly, until the original requirement surfaces — the best solution may be Z, not Y.

Counter-example: implementing an elaborate solution to Y, then discovering the user never needed Y at all.

11. Bold over conservative — innovation and practicality are not in conflict

Embrace technologies that will change the future (e.g. Docker, Go), without blindly adopting every novelty (e.g. treat blockchain/Rust with respect but caution). Progress comes from exploration, and exploration has a cost — but the cost of not exploring is higher. "Not daring to fail is the biggest failure."

Counter-example: "We are pragmatic, we don't need innovation" — such systems carry debt from day one and eventually migrate to the new technology anyway.

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Self-developed vs Open Source vs Customized Open Source

Use this framework when the question is "build it or adopt it".

Decide on three axes:

• Team resources — skill level, headcount, availability
• Team goals — out-of-the-box speed / talent-building / industry contribution
• Component suitability — maturity, stability, feature fit, performance, controllability

Self-developed: best fit to business model, usually best performance; cost is a closed tech stack, weaker community integration, and risk of a half-finished component if resources mismatch.

Open source: out-of-the-box, close to community, cheaper; cost is limited troubleshooting levers and possibly worse performance (more abstraction layers, longer execution path).

Customized open source: write plugins to fit the business model, or fork and modify non-fitting parts.

Heuristic: small teams → open source or cloud services; large teams → self-develop the core stack (and consider open-sourcing it later, e.g. TDSQL). Even well-known open-source software can have irrational designs (see the Prometheus analysis) — evaluate skeptically, because a flawed low-level design is nearly impossible to fix later.

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Relationship to other skills

• scenario-standards — this skill is invoked at its Architecture phase (tech stack selection + rationale). Apply the 11 principles to produce the "rationale" that phase requires.
• coding-tactics — parallel concern. coding-tactics selects how to write (TDD/BDD/API-First); this skill decides whether and why a design choice is right. No overlap.
• workflow-orchestrator — its review gates consume this skill as the "architecture soundness" lens. Principle 4 (completeness) and 5 (standards) map directly to review criteria.
• qa-suite — weak link. Principle 4 (completeness over performance) informs what "complete" means for test coverage; principle 5 (standards) informs test conventions.

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Internal routing contract

When invoked internally by workflow-orchestrator, do not wait for a second confirmation. Return exactly one JSON object with these fields:

json

{
  "status": "complete|blocked",
  "decision": "",
  "principles_applied": [],
  "tradeoffs": [],
  "open_questions": []
}

A blocked result MUST identify the missing or contradictory decision input in open_questions. Standalone invocation keeps the existing interactive output contract.

Output contract

When applying this skill, end with a decision summary in this shape:

1. Decision — the recommended choice and why.
2. Principles applied — which of the 11 (and the build-vs-buy framework, if relevant) drove it.
3. Trade-offs — what was sacrificed, explicitly.
4. Open questions — what data is still missing before the decision is final.