complexity-review

name	complexity-review
description	Reviews technical proposals against 30 complexity dimensions. Questions necessity of scale, consistency, and resilience. Use when proposing technologies (Kafka, microservices, event sourcing) or designing systems. Pushes for simplest viable approach.

icon: 🔍

Complexity Review

Review technical proposals by:

1. Systematically reviewing against the 30 Complexity Dimensions (see REFERENCE.md)
2. Questioning every complexity driver
3. Proposing simpler alternatives
4. Identifying what can be postponed

The 6 Complexity Categories

Use these categories to systematically challenge technical proposals. For the complete 30 dimensions checklist, see REFERENCE.md.

1. Data Volume and Nature (5 dimensions)

• Data size, number of elements, growth rate, processing weight, lifespan
• Key questions: "How much data really?", "Do we need to handle this scale now?"

2. Interaction and Frequency (4 dimensions)

• Interaction frequency, latency, concurrency, elasticity
• Key questions: "How often does this happen?", "Can we use batch instead of real-time?"

3. Consistency, Order, Dependencies (5 dimensions)

• Processing order, scope of order, consistency guarantees, distributed transactions, state
• Key questions: "Does order matter?", "Can we use eventual consistency?"

4. Resilience, Security, Fault Tolerance (8 dimensions)

• Error criticality, idempotence, side effects, uniqueness, reversibility, inconsistency tolerance, exactly-once, auditability
• Key questions: "What happens if this fails?", "Can we accept graceful degradation?"

5. Integration, External Dependencies, Versions (4 dimensions)

• External dependencies, security/privacy, versioning, interoperability
• Key questions: "Can we mock external services initially?", "Do we need versioning now?"

6. Efficiency, Maintainability, Evolution (4 dimensions)

• Refactoring flexibility, cost sensitivity, availability requirements, scaling time
• Key questions: "Can we change this later?", "Do we need 99.99% uptime or is 99% OK?"

Quick Reference: Proposal → Dimensions to Challenge

Proposal Contains	Challenge These Dimensions	Alternative to Consider
Kafka, event streaming, message queues	#6 (frequency), #10 (order), #12 (consistency), #13 (transactions)	PostgreSQL + cron job, simple polling
Microservices	#8 (concurrency), #13 (distributed transactions), #14 (state), #23 (dependencies)	Modular monolith, well-structured modules
Event sourcing, CQRS	#10 (order), #12 (consistency), #22 (auditability), #27 (refactoring)	Append-only table, structured logging
Caching layer (Redis, Memcached)	#5 (lifespan), #7 (latency), #12 (consistency), #20 (inconsistency tolerance)	In-memory cache, query optimization first
Auto-scaling, serverless	#8 (concurrency), #9 (elasticity), #28 (cost), #30 (scaling time)	Fixed capacity, manual scaling initially
NoSQL database	#2 (elements), #12 (consistency), #13 (transactions), #27 (refactoring)	PostgreSQL with JSONB, evaluate need first
Multiple databases	#23 (dependencies), #27 (refactoring), #28 (cost)	Single database with clear schema
Real-time features, WebSockets	#6 (frequency), #7 (latency), #8 (concurrency), #14 (state)	Polling, periodic refresh (5-30 sec)

Review Process

Step 1: Identify Complexity Drivers

List all the complexity dimensions the proposal addresses (scale, consistency, resilience, etc.)

Step 2: Challenge Each One

Review all 30 dimensions against the proposal. Most will pass without issue — only document the ones that raise a real concern or challenge the proposal.

For each challenge, ask:

• Is this assumption based on actual requirements or speculation?
• What's the simplest alternative that could work today?
• Can we postpone this until we have data?

Important:

• Do NOT document dimensions that pass without concern — only those that genuinely challenge the proposal.
• If a challenge needs user input to resolve, mark it as Open and present it to the user before continuing to the next challenge. Resolve challenges one at a time, like Open Questions.

Step 3: Propose Simpler Alternatives

Generate 2-3 progressively simpler versions of the proposal:

• Version 1 (Simplest): Absolute minimum, possibly manual. Must be deployable in 1-3 days.
• Version 2 (Moderate): Some automation, limited scale
• Version 3 (Proposed): Original proposal (only if justified)

Explain WHY the simpler version is better — not just "it's simpler". Include concrete criteria for when to add complexity later (e.g., "only if load > 10K/sec").

Step 4: Highlight What Can Be Postponed

List features/complexity that can be added later:

• "We can add retries later if we see failures"
• "We can scale horizontally later if load increases"
• "We can add monitoring later if this becomes critical"

Step 5: Analyze Basal Cost

For each component/feature in the proposal, estimate the ongoing cost it imposes on the team.

Basal Cost of Software

Every dimension of complexity has an ongoing cost simply by existing — not the initial build cost, but the tax you pay forever after. It accumulates, grows non-linearly with coupling, and can exhaust a team.

Components: cognitive load, testing burden, maintenance (dependencies, docs), operational overhead (monitoring, debugging), future change cost (each new feature must account for existing complexity).

If basal cost consumes 70-80% of team capacity, only 20-30% remains for new features — the team is in a capacity trap.

When reviewing any proposal, ask:

• "What's the ongoing cost of this?"
• "How much team capacity will this consume in 6 months?"
• "What's the simplest version with 10x lower basal cost?"
• "Can we remove something else to make room for this?"

When reviewing proposals

• Question every complexity driver — do not accept assumptions about scale, performance, or reliability without data
• Always ask: "Do we have data showing we need this?"
• Default to postponement: "Can we add this later when we know we need it?"
• Consider impact: "What's the worst that could happen if we don't build this?"
• Seek efficiency: "Can we achieve the same impact with fewer resources?"
• Apply time pressure: "What if we only had half the time?"

Reference

For the complete list of 30 Complexity Dimensions with detailed questions, specialized checklists, and more examples, see REFERENCE.md in this skill directory.