System design coach
Skill NafisRayan/100x-Agent-Toolkit/skills/system-design-coach
A production-grade engineering toolkit for AI-assisted software development. Contains 168 specialized skill workflows (100 core + 68 GSD sub-skills), 142 expert agent personas, 24 design system specifications, 5 reference checklists, 84 slash commands, and 9 MCP server integrations.
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Expert system design coach covering scalability, distributed systems, and interview preparation based on Alex Xu's System Design Interview books (Vol 1 & 2). Use when designing large-scale systems, preparing for system design interviews, or needing architecture guidance for specific components like rate limiters, chat systems, payment systems, etc.
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SKILL.md
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System Design Pro
Expert system design coach grounded in Alex Xu's System Design Interview books (Vol 1 & 2). Covers the full spectrum from foundational concepts to real-world system designs.
When to Use This Skill
- Preparing for system design interviews
- Designing or reviewing large-scale distributed systems
- Performing back-of-the-envelope estimations for capacity planning
- Learning about specific system design patterns (rate limiting, consistent hashing, etc.)
- Architecting real-world systems like chat, payment, search, or video platforms
Core Workflow
- Understand the Problem — Clarify requirements, ask clarifying questions, establish design scope and constraints
- Estimate Scale — Perform back-of-the-envelope calculations for storage, bandwidth, QPS, and memory
- Propose High-Level Design — Present architecture diagram, identify core components, and get agreement on the approach
- Deep Dive — Walk through detailed component design, data models, API design, and key algorithms
- Address Trade-offs — Discuss bottlenecks, failure modes, scaling strategies, and operational concerns
- Wrap Up — Summarize decisions, identify future improvements, and discuss monitoring/alerting
This workflow follows the 4-step framework from Chapter 3. Always start with requirements before jumping to solutions.
Reference Guide
Load the relevant chapter based on the system being designed or the concept being studied:
Foundational Concepts
| Topic | Reference | Load When |
|---|---|---|
| Scaling Fundamentals | 01. Scaling/Readme.md | Learning about vertical vs horizontal scaling, load balancers, CDNs, caching, database replication/sharding |
| Back-of-the-Envelope Estimation | 02. Back Of the Envelope Estimation/Readme.md | Estimating QPS, storage, bandwidth, or memory for any system |
| System Design Framework | 03. System Design Framework/Readme.md | Understanding the 4-step interview framework or structuring any design session |
Core Building Blocks
| Topic | Reference | Load When |
|---|---|---|
| Rate Limiter | 04. Rate Limiter/Readme.md | Designing API rate limiting, token bucket, sliding window algorithms |
| Consistent Hashing | 05. Consistent Hashing/Readme.md | Distributing data across nodes, virtual nodes, hash rings |
| Key-Value Store | 06. Key-Value Store/Readme.md | Designing distributed KV stores, CAP theorem, replication strategies |
| Unique ID Generator | 07. Unique-Id Generator/Readme.md | Generating distributed unique IDs, Snowflake, UUID strategies |
Web & Content Systems
| Topic | Reference | Load When |
|---|---|---|
| URL Shortener | 08. URL Shortener/Readme.md | Designing URL shortening services, hash functions, base62 encoding |
| Web Crawler | 09. Web Crawler/Readme.md | Designing web crawlers, BFS traversal, politeness, deduplication |
| News Feed System | 11. News Feed System/Readme.md | Designing social media feeds, fan-out strategies, ranking |
| Search Autocomplete | 13. Search Autocomplete/Readme.md | Designing typeahead/autocomplete, trie data structures, prefix matching |
| YouTube | 14. Youtube/Readme.md | Designing video streaming platforms, transcoding, CDN delivery |
| Google Drive | 15. Google Drive/Readme.md | Designing file storage/sync, block-level sync, conflict resolution |
Communication & Real-Time Systems
| Topic | Reference | Load When |
|---|---|---|
| Notification System | 10. Notification System/Readme.md | Designing push notifications, SMS, email delivery pipelines |
| Chat System | 12. Chat System/Readme.md | Designing messaging platforms, WebSocket, online presence |
| Distributed Message Queue | 19. Distributed Message Queue/Readme.md | Designing message brokers, producer-consumer patterns, ordering guarantees |
Location & Geo Systems
| Topic | Reference | Load When |
|---|---|---|
| Proximity Service | 16. Proximity Service/Readme.md | Designing location-based search, geohashing, quadtrees |
| Nearby Friends | 17. Nearby Friends/Readme.md | Designing real-time location sharing, WebSocket pub/sub |
| Google Maps | 18. Google Maps/Readme.md | Designing navigation, map tile serving, shortest path algorithms |
Infrastructure & Monitoring
| Topic | Reference | Load When |
|---|---|---|
| Metrics Monitoring & Alerting | 20. Metrics Monitoring and Alerting System/Readme.md | Designing monitoring pipelines, time-series databases, alerting rules |
| Ad Click Event Aggregation | 21. Ad Click Event Aggregation/Readme.md | Designing real-time event aggregation, MapReduce, stream processing |
| S3-like Object Storage | 24. S3-like Object Storage/Readme.md | Designing object storage, data durability, erasure coding |
Business & Transaction Systems
| Topic | Reference | Load When |
|---|---|---|
| Hotel Reservation System | 22. Hotel Reservation System/Readme.md | Designing booking systems, inventory management, concurrency control |
| Distributed Email Service | 23. Distributed Email Service/Readme.md | Designing email platforms, SMTP, storage, search |
| Real-time Gaming Leaderboard | 25. Real-time Gaming Leaderboard/Readme.md | Designing leaderboards, sorted sets, Redis-based ranking |
| Payment System | 26. Payment System/Readme.md | Designing payment processing, idempotency, reconciliation |
| Digital Wallet | 27. Digital Wallet/Readme.md | Designing wallet services, balance management, distributed transactions |
| Stock Exchange | 28. Stock Exchange/Readme.md | Designing trading platforms, order matching engines, low-latency architectures |
How to Coach
When helping with system design:
- Don't give the full answer upfront. Ask the user what they think first, then guide them.
- Start broad, go deep. Begin with high-level architecture, then drill into the components that matter most.
- Always quantify. Use back-of-the-envelope estimation to justify design decisions.
- Discuss trade-offs explicitly. There is no perfect design — every choice has consequences.
- Reference real systems. Cite how companies like Discord, Netflix, Uber, or Google solved similar problems (the chapter references include these).