Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/orlando-japan/claude-code-setting/system-designnpx skills add orlando-japan/claude-code-setting --skill system-designgit clone --depth 1 https://github.com/orlando-japan/claude-code-settingWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/orlando-japan/claude-code-setting/system-design)<a href="https://agentmods.dev/skills/orlando-japan/claude-code-setting/system-design"><img src="https://agentmods.dev/badge/skills/orlando-japan/claude-code-setting/system-design.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00028 | $0.00808 |
| Opus 5 | $0.00014 | $0.00404 |
| Sonnet 5 | $0.00006 | $0.00162 |
| Haiku 4.5 | $0.00003 | $0.00081 |
Grade A, and why
system-design scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 92 lines — stays where its author put it; the contents beside it link to each section on GitHub.
System design
The goal is a design you can defend — not the cleverest option, the one that holds up to questioning.
The 6-step frame
1. Clarify requirements
Two lists:
- Functional: what must the system do? Enumerate the actual user interactions.
- Non-functional: how fast, how reliable, how much data, how many users, how private?
If you don't have numbers, make them up explicitly: "assume 1k RPS, 10M rows, p99 <200ms." Wrong numbers you can iterate on; absent numbers you can't.
2. Estimate capacity
Back-of-envelope, not precision:
- Reads / writes per second
- Storage (rows × average size × retention)
- Network egress
- Peak vs steady state
This is where impossible requirements get exposed. "1M writes/sec to a single Postgres instance" stops the conversation before you start coding.
3. Data model
- What entities? What are their IDs?
- What relationships? One-to-many, many-to-many, hierarchical?
- What access patterns? Read by ID, scan by timestamp, aggregate by user?
- Pick storage to fit. Access patterns drive DB choice, not preference.
4. API / interfaces
- Inputs and outputs for each operation.
- Sync vs async (request/response vs queue).
- Pagination, rate limits, idempotency.
- Auth and authz model.
5. Architecture sketch
- Components (services, DBs, queues, caches).
- Data flow for the two or three most important operations (draw it).
- Where's the state?
- What's stateless?
- Where are the failure domains?
6. Trade-offs and open questions
For each major choice, name the alternative and why you rejected it. Be honest about open questions — "we haven't decided how to handle X" is fine; pretending X is solved is not.
Non-functional thinking
For each requirement, ask: "what does this mean concretely?"
- "Highly available" → 99.9%? 99.99%? What's the downtime budget? What happens during a region outage?
- "Scales well" → to what? From what? Vertically? Horizontally? Shardable?
- "Fast" → p50 or p99? Measured from where?
- "Secure" → against what threat? From whom?
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 5d ago First seen · 92 lines · 28 tokens per session scan A df140b114da0
system-design is a skill published in the GitHub repository orlando-japan/claude-code-setting (2 stars, last pushed 3mo ago), licensed MIT. It adds 28 tokens to every session and 808 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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