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Module 20: The Interview Battleground — System Design Cases

🚀 Purpose

This module ties everything together with 10 system design problems calibrated for senior/staff-level interviews, each with a GenAI twist relevant to real-world engineering challenges.

📋 Practice Problems

# Problem Core Concepts Tested Time
1 Design a Document Processing Pipeline Event streaming, data pipelines, saga patterns 45 min
2 Design a RAG-based Q&A System at Scale Vector search, hybrid retrieval, caching, LLM orchestration 45 min
3 Design a Multi-Tenant AI Platform Tenant isolation, rate limiting, cost allocation, data residency 45 min
4 Design a Real-Time Collaborative Document Editor CRDTs/OT, WebSocket, conflict resolution 45 min
5 Design a URL Shortener (classic, warm-up) Hashing, caching, analytics, rate limiting 30 min
6 Design a Notification System Queue, fan-out, delivery guarantees, user preferences 30 min
7 Design an AI-Powered Code Review System ML serving, streaming, feedback loops 45 min
8 Design a Semantic Search Engine Inverted index, HNSW, hybrid search, re-ranking 45 min
9 Design an LLM Gateway / AI Proxy Rate limiting, model routing, cost controls, fallback chains 45 min
10 Design a Compliance Audit System Event sourcing, immutable logs, access control, versioning 45 min

🎯 Interview Framework (Use for Every Problem)

1. CLARIFY (2 min)
   → Users, scale, latency requirements, cost constraints

2. HIGH-LEVEL DESIGN (5 min)
   → Draw 5-7 boxes, label data flows, identify the "hard part"

3. DEEP DIVE (20 min)
   → Focus on 2-3 components the interviewer cares about
   → Always discuss: data model, API design, scaling bottleneck

4. TRADE-OFFS (5 min)
   → "We could also do X, but Y is better here because..."
   → Demonstrate that alternatives were considered and rejected

5. OPERATIONAL CONCERNS (3 min)
   → Monitoring, failure modes, deployment strategy
   → "If this component fails, here's what happens and how we recover"

🔗 Case Study References