What is nw-sd-case-studies?

A reference guide containing 25 real-world system design case studies, such as rate limiters, key-value stores, and messaging systems. Each case explains requirements, architecture, and important design choices.

It helps compare architecture options, study common distributed-system designs, and prepare for system design interviews.

It provides prior examples when you need to design a system but are unsure which structures and trade-offs to consider.

nw-sd-case-studies — Skill for Claude Code by nWave-ai/nWave

Install

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.

Any agent

npx skills add nWave-ai/nWave --skill nw-sd-case-studies

Clone the repo

git clone --depth 1 https://github.com/nWave-ai/nWave

Made for: Claude Code.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/nwave-ai/nwave/nw-sd-case-studies/github.svg)](https://agentmods.dev/skills/nwave-ai/nwave/nw-sd-case-studies)

Your own site

<a href="https://agentmods.dev/skills/nwave-ai/nwave/nw-sd-case-studies"><img src="https://agentmods.dev/badge/skills/nwave-ai/nwave/nw-sd-case-studies/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/nwave-ai/nwave/nw-sd-case-studies"><img src="https://agentmods.dev/badge/skills/nwave-ai/nwave/nw-sd-case-studies.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 40 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,865 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector pass 7 Sept 2026

How audits are shown

Origin original No closer match found in the catalogue.

Token cost

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	$0.00040	$0.02865
Opus 5.5	$0.00016	$0.01146
Sonnet 5.5	$0.00008	$0.00573
Haiku 4.5	$0.00004	$0.00286

Measured 2mo ago against content hash fe998efd26c5, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

nw-sd-case-studies 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 2mo 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.

nWave/skills/nw-sd-case-studies/SKILL.md · 110 lines

How it starts

The opening of the file, as written. The whole thing — 110 lines — stays where its author put it; the contents beside it link to each section on GitHub.

System Design Case Studies

Reference catalog of 25 real-world designs. Use when designing a similar system or needing precedent for architectural decisions.

Volume 1 Case Studies

Rate Limiter

Scale: API gateway middleware | Core: Token Bucket (industry standard) or Sliding Window Counter | Storage: Redis counters with TTL | Distributed: Lua scripts for atomic increment | Key insight: cross-cutting concern, belongs in middleware/gateway | Headers: 429 + Retry-After + X-RateLimit-Remaining

Consistent Hashing

Core: hash ring 0 to 2^32-1, servers at positions, keys walk clockwise | Virtual nodes: 100-200 per server, reduces load deviation from ~40% to ~5% | Used in: DynamoDB, Cassandra, Akamai, Discord | Key insight: never deploy without virtual nodes

Key-Value Store (Dynamo-style)

Core: consistent hashing for partitioning, N replicas on clockwise nodes, quorum W+R>N | Conflict: vector clocks, LWW, app-level merge | Failures: sloppy quorum + hinted handoff (temp), Merkle trees + anti-entropy (permanent), gossip for detection | Write path: WAL -> memtable -> SSTable (LSM-tree) | Read path: memtable -> Bloom filter -> SSTable(s)

Unique ID Generator

URL Shortener

Scale: 100M/day ~ 1,160 QPS write, 11,600 read | Short URL: base62 with 7 chars = 3.5T combinations | Approaches: hash + collision resolution | base62 from auto-increment ID | pre-generated key service | Redirect: 301 (cached, no analytics) vs 302 (every click tracked) -- most use 302 | Key: caching critical (heavy-tailed distribution)

Web Crawler

Scale: 1B pages/month ~ 400 pages/sec, 500TB storage/month | Core: URL Frontier with priority queues (importance) + politeness queues (per-domain rate limit) | Dedup: SHA-256 exact, simhash/MinHash near-duplicate | Traps: URL length limit, max depth, blacklist | Key insight: URL frontier is the most important component

Read the full file on GitHub · 110 lines

Changes

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.

2mo ago First seen · 110 lines · 40 tokens per session scan A fe998efd26c5

Subscribe to this mod's changes

nw-sd-case-studies is a skill published in the GitHub repository nWave-ai/nWave (631 stars, last pushed yesterday), licensed MIT. It adds 40 tokens to every session and 2,865 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-09-06.

Backend and APIs Claude Code DevOps and cloud Learning and teaching TDD agentic-ai ai software-architecture

nw-sd-case-studies next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
nw-sd-case-studiesnWave-ai/nWave	Skill	631	yesterday	MIT	A	40	Claude Code
backend-developmentsaajunaid/caddis-plugin	Skill	0	yesterday	MIT	A	22	Claude Code, Codex
RabbitAdvisors 知识付费案例研究microwind/ai-skills	Skill	93	5mo ago	none	A	50	Claude Code, Codex
限界上下文microwind/ai-skills	Skill	93	5mo ago	none	A	32	Claude Code, Codex
上下文映射microwind/ai-skills	Skill	93	5mo ago	none	A	32	Claude Code, Codex
领域模型microwind/ai-skills	Skill	93	5mo ago	none	A	28	Claude Code, Codex
聚合 (Aggregate)microwind/ai-skills	Skill	93	5mo ago	none	A	32	Claude Code, Codex