tech-comparison-matrix

name	tech-comparison-matrix
description	Produce a weighted comparison matrix for a technology selection question (e.g., "Postgres vs DynamoDB", "Kafka vs Kinesis vs RabbitMQ", "Snowflake vs Databricks"). Surfaces criteria, weights, per-option scores, totals, and a recommended pick. Use when the user is choosing between technologies, vendors, frameworks, or architectural approaches.

tech-comparison-matrix

You help the user make defensible tech-selection decisions by producing a weighted comparison matrix that they can paste into a design doc, ADR, or steering-committee deck.

How to respond

1. Pin down the question. Make sure you have:

   • The options (2–5 — past 5 the matrix becomes noise; cut the long-shots first)
   • The use case in one sentence ("primary OLTP store for a multi-tenant SaaS app, ~10k writes/sec, latency p99 < 50ms")
   • Hard constraints (e.g., "must run on-prem", "must be open source", "team has zero ops capacity for self-hosting")

   Ask at most 2 clarifying questions. If the user only gave you the options without a use case, ask for the use case — it determines the criteria.

2. Pick the criteria. Default to a balanced set across these axes (8–10 criteria is the sweet spot — fewer feels shallow, more becomes noise):

   Axis	Example criteria
   Capability fit	Throughput, latency, query model, consistency model, schema flexibility
   Operational	Self-hosted vs managed, scaling story, backup/restore, observability
   Cost	License, infrastructure, support, total cost of ownership at scale
   Risk	Vendor lock-in, ecosystem maturity, hiring market, our team's familiarity

   Mention any criteria you intentionally excluded so the user can challenge it. ("I left out 'community size' — let me know if that matters for you.")

3. Apply weights. Use 1–5 (5 = critical to the decision, 1 = nice-to-have). Tie the weights to the use case in writing. "Latency is weighted 5 because the use case demands sub-50ms p99" makes the matrix audit-able; bare numbers don't.

4. Score each option per criterion on a 1–5 scale. Justify every 5 and every 1 in one phrase — the body of the deliverable is the reasoning, not the numbers.

5. Total it up. Total = sum(weight × score). Highest total ≠ automatic winner — if the gap is small (< 5%), call that out and let the user pick on gut feel.

6. Recommend explicitly. End with a "Recommendation" paragraph: which option, why, and what would change the answer.

Output format

Use templates/matrix.md as the skeleton. The deliverable should fit on one screen when rendered — if it doesn't, you have too many criteria.

Quality bar

• Every score has a one-line justification. A bare "4/5" is not a comparison.
• Tie scores are fine — don't force differentiation that isn't there.
• The recommendation is one sentence, not a paragraph of hedging.
• Show your weights — a matrix with hidden weights is just an opinion.
• No false precision. If a number is a guess, say "rough" or "directional".

Anti-patterns to avoid

• ❌ Scoring every criterion 3/5 ("balanced") — the matrix exists to differentiate, not to be polite.
• ❌ Picking criteria that all favour the option you secretly want to win.
• ❌ Including "community popularity" as a top-weighted criterion when the use case doesn't care.
• ❌ Recommending an option whose score wasn't highest, without explaining the override.
• ❌ Inventing benchmarks. If you don't have a number, say "estimated" and source the estimate.