System Design - SDE-3 Guide

Comprehensive, streamlined system design guide for senior/staff engineer interviews Consolidating best practices, advanced patterns, and real-world implementations

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About This Repository

This repository is optimized for SDE-3 level interview preparation (Senior/Staff Software Engineer). It consolidates system design concepts, eliminates duplicate content, and provides in-depth insights with production-level trade-offs.

What's New (v2.0)?

• Consolidated Content: Merged duplicate topics from multiple sources

• Advanced Topics: Distributed systems, consensus protocols, consistency models, idempotency/retry/backpressure

• Interview Templates: Step-by-step HLD/LLD interview frameworks

• SYSTEM_DESIGN_INTERVIEW_FRAMEWORK.md: How to approach the interview (clarify → estimate → HLD → bottlenecks → trade-offs → deep dive → scaling/failure)

• SYSTEM_DESIGN_REPO_AUDIT.md: Full audit of repo coverage and recommended additions

• Building Blocks: Dedicated deep dives for load balancers, reverse proxy, CDN, caching, message brokers, service discovery, API gateway, distributed locks, rate limiting, sharding, replication

• Scaling Strategies: Horizontal vs vertical, DB scaling, replication, partitioning, caching, queues, async

• Cheat Sheets: Quick reference for capacity estimation & trade-offs

• Enhanced Problems: HLD problems including Search System; capacity estimation & scaling strategies

• Production Focus: Real-world examples, Senior Engineer Insights, Quick Revision sections, and operational trade-offs

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Repository Structure

SystemDesign/
├── SYSTEM_DESIGN_REPO_AUDIT.md        # Repo audit & recommended additions
├── SYSTEM_DESIGN_INTERVIEW_FRAMEWORK.md # How to approach system design interviews
├── core-concepts/                     # Fundamental building blocks
│   ├── fundamentals.md                # Complete basics (networking, protocols, caching, etc.)
│   ├── databases.md                    # SQL vs NoSQL, ACID, CAP, replication, sharding
│   ├── caching-cdn.md
│   ├── networking.md
│   └── security.md
│
├── building-blocks/                    # Deep dives: LB, proxy, CDN, cache, brokers, discovery, gateway, locks, rate limit, sharding, replication
│   └── README.md + individual docs
├── scaling/                            # Scaling strategies (horizontal/vertical, DB, replication, caching, queues)
│   ├── README.md
│   └── scaling-strategies.md
├── advanced-topics/                    # SDE-3 level deep dives
│   ├── distributed-systems.md          # Consistency models, consensus, time & ordering
│   ├── distributed-concepts.md          # Idempotency, retry, backpressure
│   ├── observability.md                # Metrics, tracing, SLI/SLO/SLA
│   └── chaos-engineering.md
│
├── hld-problems/                       # System design problems (easy/medium/hard)
│   ├── README.md                       # Problem catalog & difficulty ratings
│   ├── easy/                           # URL Shortener, Pastebin, etc.
│   ├── medium/                         # Twitter, Instagram, etc.
│   └── hard/                           # Uber, Netflix, Distributed Message Queue
│
├── lld-problems/                       # Low-level design & patterns
│   ├── design-patterns/
│   ├── SOLID-principles/
│   ├── concurrency/
│   └── problems/
│
├── interview-templates/                # Frameworks for interviews
│   ├── hld-template.md                 # 45-60 min HLD interview guide
│   ├── lld-template.md                 # LLD approach checklist
│   ├── capacity-estimation.md          # QPS, storage, bandwidth calculations
│   └── trade-offs-cheat-sheet.md       # SQL vs NoSQL, sync vs async, etc.
│
└── reference/                          # Quick reference materials
    ├── numbers-to-know.md              # Latency, throughput, cost estimates
    ├── ml-system-design.md
    └── book-summaries/

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Learning Paths

Path 1: Beginner to Intermediate (4-6 weeks)

Goal: Build strong foundation in system design concepts

Week 1-2: Core Concepts

• Read core-concepts/fundamentals.md

  • Networking: IP, DNS, TCP/UDP, HTTP/HTTPS

  • Load balancing, caching, CDN

  • Availability, scalability, reliability

• Read core-concepts/databases.md

  • SQL vs NoSQL decision matrix

  • ACID vs BASE

  • CAP theorem

Week 3-4: Practice Easy Problems

• URL Shortener (hld-problems/easy/)

• Pastebin

• Key-Value Store

• Use interview-templates/hld-template.md for structured approach

Week 5-6: Intermediate Concepts

• Read core-concepts/caching-cdn.md

• Practice medium problems:

  • Twitter Timeline

  • Instagram

  • Notification Service

Resources:

• interview-templates/capacity-estimation.md for back-of-envelope calculations

• interview-templates/trade-offs-cheat-sheet.md for decision-making

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Path 2: SDE-3 Interview Preparation (6-8 weeks)

Goal: Master advanced topics and complex system design

Week 1-2: Master Core Concepts

• Review all files in core-concepts/

• Focus on trade-offs and production scenarios

Week 3-4: Advanced Distributed Systems

• advanced-topics/distributed-systems.md

  • Consistency models (strong, eventual, causal)

  • Lamport/Vector clocks

  • CRDTs, conflict resolution

• advanced-topics/consensus-protocols.md

  • Raft consensus (step-by-step)

  • Paxos algorithm

  • When to use each

Week 5-6: Distributed Transactions & Patterns

• advanced-topics/distributed-transactions.md

  • Two-Phase Commit (2PC)

  • Saga pattern (choreography vs orchestration)

  • Outbox pattern

• Practice hard problems:

  • Distributed Message Queue

  • Payment System

  • Stock Exchange

Week 7-8: Mock Interviews & Refinement

• Practice all 27 HLD problems

• Use interview-templates/hld-template.md for every problem

• Time yourself (45-60 min per problem)

• Focus on:

  • Capacity estimation (first 15 min)

  • Trade-offs (SQL vs NoSQL, sync vs async)

  • Scaling strategies

  • Failure scenarios

Key Files for SDE-3:

1. interview-templates/capacity-estimation.md → Master QPS, storage, bandwidth calculations

2. interview-templates/trade-offs-cheat-sheet.md → Decision matrices for all major choices

3. advanced-topics/distributed-systems.md → Understand consistency vs availability deeply

4. reference/numbers-to-know.md → Memorize latency numbers

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Path 3: Staff/Principal Engineer (Advanced)

Goal: Deep expertise in distributed systems and production operations

Focus Areas:

• advanced-topics/observability.md

  • Distributed tracing (Jaeger, Zipkin)

  • SLI/SLO/SLA definitions with math

  • Alert fatigue prevention

• advanced-topics/chaos-engineering.md

  • Resilience patterns

  • Production testing strategies

• Advanced problem variants:

  • Multi-region active-active

  • Cross-datacenter consensus

  • Handling network partitions

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Interview Preparation Checklist

Before the Interview

• Review interview-templates/hld-template.md (know the 7 phases)

• Memorize numbers from reference/numbers-to-know.md

  • 1M requests/day ≈ 12 QPS

  • L1 cache: 0.5ns, RAM: 100ns, SSD: 150μs

  • 99.9% availability = 8.76 hours downtime/year

• Practice capacity estimation (use 5 Interview Templates/capacity-estimation.md)

• Review trade-offs (use interview-templates/trade-offs-cheat-sheet.md)

During the Interview

Phase 1 (0-10 min): Requirements

• Clarify functional requirements (top 3-5 features)

• Define non-functional requirements (PASS-R: Performance, Availability, Scalability, Security, Reliability)

• Agree on scale (DAU, QPS, storage)

Phase 2 (10-15 min): Capacity Estimation

• Calculate QPS (writes, reads)

• Estimate storage (per record × total records × replication)

• Bandwidth (QPS × response size)

Phase 3 (15-25 min): Design

• API design (REST endpoints)

• Database schema

• High-level architecture diagram

Phase 4 (25-55 min): Deep Dives

• Scaling strategies

• Caching approach

• Failure scenarios

• Trade-offs (SQL vs NoSQL, sync vs async, etc.)

Phase 5 (55-60 min): Wrap-up

• Summars design

• Mention future enhancements

• Q&A

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Key Principles for SDE-3 Interviews

1. Always Discuss Trade-offs

Don't just say "I'd use Redis for caching." Say:

"I'd use Redis for caching because:

• Sub-millisecond latency (critical for our 100ms SLA)

• Rich data structures (sorted sets for leaderboards)

• Limited storage (use LRU eviction)

• Not durable (persist to DB as source of truth)"

2. Think at Scale

• Start simple, then scale

• "For 1K users, single server works. At 1M users, we need..."

• Use real numbers (capacity estimation)

3. Production Mindset

• Monitoring: "How do we know it's working?"

• Failure scenarios: "What if the DB goes down?"

• Operational complexity: "How hard is this to maintain?"

4. Communication

• Think out loud

• Draw diagrams

• Ask clarifying questions

• Validate assumptions with interviewer

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Recommended Study Order

1. Start here: interview-templates/hld-template.md

2. Learn basics: core-concepts/fundamentals.md

3. Master databases: core-concepts/databases.md

4. Practice estimation: interview-templates/capacity-estimation.md

5. Learn trade-offs: interview-templates/trade-offs-cheat-sheet.md

6. Advanced topics: advanced-topics/distributed-systems.md

7. Practice problems: hld-problems/ (start easy → hard)

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Migration from Old Structure

If you're familiar with the old repository structure:

Old Location	New Location
system-design-hld+lld/hld/basics.md	core-concepts/fundamentals.md
glossary.md + system-design-components.md	core-concepts/databases.md
30-days-theory/	Removed (content integrated into Core Concepts)
hld/notes/interview-process/	hld-problems/
lld/lld-interview-guide.md	interview-templates/lld-template.md

What was removed:

• Duplicate content (glossary, repeated design patterns)

• 30-days-theory (integrated into core concepts)

• Scattered interview questions (now organized by difficulty)

What was added:

• Advanced distributed systems topics

• Interview templates with timing

• Capacity estimation formulas

• Trade-off decision matrices

• Enhanced problem descriptions with capacity estimation

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How to Use This Repository

For Interview Preparation

# Clone the repository
git clone https://github.com/yourusername/SystemDesign.git
cd SystemDesign

# Start with interview template
cat "interview-templates/hld-template.md"

# Practice a problem using the template
# Example: Design URL Shortener
open "hld-problems/easy/url-shortener.md"

# Reference cheat sheets during practice
open "interview-templates/capacity-estimation.md"
open "interview-templates/trade-offs-cheat-sheet.md"

For Learning

Follow the learning paths above based on your current level.

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Contributing

This repository is under active development. Contributions welcome!

To-Do List

• Complete all 27 HLD problem enhancements (capacity estimation, scaling, failures)

• Add LLD template with examples

• Create observability.md

• Add chaos-engineering.md

• Create practice roadmap (30-day, 60-day plans)

• Add mermaid diagrams for architecture visualizations

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Additional Resources

Books

• "Designing Data-Intensive Applications" by Martin Kleppmann

• "System Design Interview" by Alex Xu

• "Web Scalability for Startup Engineers" by Artur Ejsmont

Online

• High Scalability Blog

• AWS Architecture Center

• Google Cloud Architecture Center

Related Repositories

• System Design Primer

• Awesome System Design

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License

MIT License - Feel free to use this for your interview preparation and share with others!

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Star This Repository

If you find this helpful, please star ⭐ the repository and share with others preparing for senior-level interviews!

Good luck with your interviews!