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🖥️ Computer Science — Staff-Level Interview Questions

8 deep-dive CS topics for Staff/Principal Engineer backend interviews \ Each topic contains 9–15 questions, plus deep-dive companion pages, with code examples, diagrams, and staff-level analysis

📋 Topic Overview

cs-interview/
├── README.md                           ← You are here
│
├── operating-systems/                  ← Memory, processes, I/O, scheduling
│   └── INTERVIEW_QUESTIONS.md          (12 questions)
│
├── computer-networks/                  ← TCP/IP, HTTP/2/3, DNS, TLS, load balancing
│   └── INTERVIEW_QUESTIONS.md          (12 questions)
│
├── database-systems/                   ← B-Trees vs LSM, MVCC, replication, sharding
│   ├── INTERVIEW_QUESTIONS.md          (14 questions)
│   ├── POSTGRESQL_DEEP_DIVE.md         (13 sections: internals, tuning, operations, 12 interview questions, PG 17–18 changes)
│   └── DYNAMODB_DEEP_DIVE.md           (13 sections: keys, indexes, single-table design, bulk scenarios)
│
├── distributed-systems/                ← CAP, Raft, gossip, distributed transactions
│   ├── INTERVIEW_QUESTIONS.md          (12 questions)
│   └── DISTRIBUTED_TRANSACTION_PATTERNS.md (12 sections: 2PC, saga, outbox, TCC, idempotency)
│
├── concurrency-parallelism/            ← Lock-free, memory models, schedulers
│   └── INTERVIEW_QUESTIONS.md          (9 questions)
│
├── data-structures-algorithms/         ← Bloom filters, sketches, Merkle trees
│   ├── INTERVIEW_QUESTIONS.md          (10 questions)
│   └── DATA_STRUCTURES_FOR_SCALE.md    (12 structures)
│
├── software-architecture/              ← DDD, modular monolith, event-driven, CQRS/ES, migrations, API compatibility, ADRs
│   ├── INTERVIEW_QUESTIONS.md          (15 questions)
│   └── DESIGN_PATTERNS.md              (12 GoF patterns in 11 sections + selection framework)
│
└── security/                           ← OWASP, JWT, OAuth2, secrets management
    └── INTERVIEW_QUESTIONS.md          (10 questions)

🎯 Target Audience

Level Years Exp What's Expected
Senior 5–8 Deep understanding of one topic area
Staff 8–12 Cross-cutting knowledge across ALL topics
Principal 12+ Production war stories, trade-off mastery, ability to design from scratch

📖 How to Use

  1. Pick a topic you're weaker on
  2. Read the question and attempt to answer aloud
  3. Study the answer — pay attention to trade-offs, not just the "right" answer
  4. Trace the code examples — run them mentally, understand every edge case
  5. Connect topics — e.g., "How does the OS's page cache affect database performance?"

🔗 Cross-Cutting Themes

Theme Appears In
Caching OS (page cache), Networks (CDN), Databases (buffer pool), Distributed (caches)
Consistency vs Availability Databases (CAP), Distributed (PACELC), Architecture (eventual consistency)
Concurrency Control OS (locks), DB (MVCC), Distributed (consensus), Concurrency (lock-free)
Latency at Scale Networks (TCP), DB (query opt), Distributed (RTT), Architecture (CQRS)
Fault Tolerance Distributed (Raft), Architecture (circuit breakers), Security (redundancy)

Master these topics and you'll be prepared for the most rigorous Staff/Principal engineer interviews at FAANG, tier-2 tech, and high-growth startups.