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System Design Interview Questions

57+ system design questions organized by category, with difficulty levels and the companies that ask them. Master these to ace your FAANG system design interviews.

Social Media & Content

7 questions
1

Design Instagram

Hard
Feed Generation
Blob Storage
CDN
Database Sharding
Asked at:Meta,Google,Amazon
2

Design Instagram Stories

Hard
Ephemeral Content
Media Upload
Viewing Metrics
Discovery
Asked at:Meta,Snapchat
3

Design Twitter/X

Hard
Timeline
Fan-out
Caching
Search
Trends
Asked at:Twitter,Meta,Google
4

Design Facebook News Feed

Hard
Ranking Algorithm
Fan-out on Write/Read
Caching
Asked at:Meta,LinkedIn,TikTok
5

Design Facebook Live Video Streaming

Hard
Low-latency Streaming
Real-time Transcoding
Chat and Reactions
CDN
Asked at:Meta,Google
6

Design TikTok/YouTube Shorts

Hard
Video Processing
Recommendation
CDN
Infinite Scroll
Asked at:TikTok,Google,Meta
7

Design Reddit

Medium
Voting System
Nested Comments
Subreddits
Hot/Top Ranking
Asked at:Reddit,Amazon

Messaging & Communication

5 questions
1

Design WhatsApp/Messenger

Hard
Real-time Messaging
WebSockets
Message Queue
Presence
E2E Encryption
Asked at:Meta,Google,Microsoft
2

Design Facebook Messenger

Hard
Real-time messaging
Message delivery guarantees
Read receipts and typing indicators
Group chats at scale
Asked at:Meta,Google
3

Design Slack

Hard
Channels
Real-time Updates
Search
File Sharing
Notifications
Asked at:Slack,Microsoft,Google
4

Design Discord

Hard
Voice Chat
Server Architecture
Real-time
Bot Integration
Asked at:Discord,Google
5

Design a Notification System

Medium
Push Notifications
Priority Queue
Rate Limiting
Multi-channel
Asked at:Amazon,Meta,Google

Video & Streaming

5 questions
1

Design YouTube

Hard
Video Transcoding
CDN
Recommendation
Adaptive Streaming
Comments
Asked at:Google,Netflix,Amazon
2

Design Netflix

Hard
Streaming
Personalization
CDN
Microservices
A/B Testing
Asked at:Netflix,Amazon,Disney
3

Design Amazon Prime Video Streaming

Hard
Video encoding and transcoding
CDN and edge caching
Adaptive bitrate streaming
Global content delivery
Asked at:Amazon,Google
4

Design Zoom/Google Meet

Hard
WebRTC
SFU/MCU
Screen Sharing
Recording
Asked at:Google,Microsoft,Zoom
5

Design Twitch

Hard
Live Streaming
Chat
Donations
Low Latency
Asked at:Amazon,Google

E-Commerce & Marketplace

6 questions
1

Design Amazon E-commerce

Hard
Product Catalog
Search
Cart
Inventory
Recommendations
Asked at:Amazon,Walmart,Shopify
2

Design Amazon's Product Recommendation System

Hard
Collaborative filtering
Content-based
Real-time vs batch
Cold start
Scale
Asked at:Amazon,Google,Meta
3

Design an Order Management System

Hard
Order lifecycle
State machine
Inventory and reservations
Payment integration
Distributed transactions
Asked at:Amazon,Walmart,Shopify
4

Design an Inventory Management System

Medium
Stock Tracking
Reservations
Distributed Locks
Consistency
Asked at:Amazon,Walmart
5

Design a Flash Sale System

Hard
High Concurrency
Rate Limiting
Queue
Inventory Lock
Asked at:Amazon,Alibaba
6

Design Airbnb

Hard
Search
Booking
Availability
Reviews
Geospatial
Asked at:Airbnb,Booking.com

Transportation & Location

9 questions
1

Design Uber/Lyft

Hard
Geospatial Index
Matching Algorithm
Real-time Location
ETA
Pricing
Asked at:Uber,Lyft,DoorDash
2

Design Uber's Ride Matching System

Hard
Geospatial indexing
Real-time driver location
Matching algorithm
ETA
Surge conditions
Asked at:Uber,Lyft
3

Design Real-Time ETA Prediction

Hard
Historical trip data
ML model serving
Live traffic
Route optimization
Low-latency at scale
Asked at:Uber,Lyft,Google
4

Design Uber Eats Search & Discovery

Hard
Restaurant search
Ranking and personalization
Geospatial filtering
Real-time menu and pricing
Caching
Asked at:Uber,DoorDash,Instacart
5

Design a Real-Time Driver Location Service

Hard
GPS stream ingestion
Pub/sub
Geospatial indexing
Nearest-neighbor queries
Privacy
Asked at:Uber,Lyft,Google
6

Design Google Maps

Hard
Graph Algorithms
Tile Rendering
Traffic Data
Navigation
Asked at:Google,Apple,Uber
7

Design DoorDash/Uber Eats

Hard
Three-sided Marketplace
Dispatch
ETA
Batching
Asked at:DoorDash,Uber,Instacart
8

Design Surge Pricing / Dynamic Pricing

Hard
Demand-Supply
Real-time Pricing
Geospatial Heatmaps
Rate Limiting
Asked at:Uber,Lyft,DoorDash
9

Design Real-time Location Tracking

Hard
WebSockets
Geospatial Index
ETA
Scalability
Asked at:Uber,Lyft,Google

Collaboration & Real-time

1 questions
1

Design Google Docs (Real-Time Collaboration)

Hard
Operational transformation or CRDTs
Real-time sync
Conflict resolution
Offline support
Asked at:Google,Microsoft

Infrastructure & Storage

3 questions
1

Design Dropbox/Google Drive

Hard
File Sync
Chunking
Deduplication
Conflict Resolution
Asked at:Google,Dropbox,Microsoft
2

Design a Distributed File System (GFS)

Hard
Chunk Servers
Master Server
Replication
Consistency
Asked at:Google,Amazon,Meta
3

Design a Distributed Cache (Redis)

Hard
Consistent Hashing
Replication
Eviction Policies
Cluster Mode
Asked at:Amazon,Google,Netflix

Search & Discovery

4 questions
1

Design Google Search

Hard
Web Crawling
Indexing
PageRank
Query Processing
Asked at:Google,Microsoft,Amazon
2

Design a Web Crawler

Medium
BFS/DFS
URL Frontier
Politeness
Deduplication
Asked at:Google,Amazon
3

Design Typeahead/Autocomplete

Medium
Trie
Caching
Ranking
Personalization
Asked at:Google,Amazon,LinkedIn
4

Design Elasticsearch

Hard
Inverted Index
Sharding
Relevance Scoring
Asked at:Elastic,Amazon

Payments & Finance

3 questions
1

Design a Payment System (Stripe)

Hard
Idempotency
Distributed Transactions
Fraud Detection
PCI Compliance
Asked at:Stripe,PayPal,Square
2

Design Venmo/PayPal

Hard
P2P Transfers
Balance Management
Transaction History
Asked at:PayPal,Square,Meta
3

Design a Stock Trading System

Hard
Order Matching
Low Latency
FIFO Queue
Market Data
Asked at:Robinhood,Bloomberg

Utility Services

4 questions
1

Design a URL Shortener (TinyURL)

Medium
Hashing
Database
Caching
Analytics
Expiration
Asked at:Google,Amazon,Meta
2

Design a Rate Limiter

Medium
Token Bucket
Sliding Window
Distributed Systems
Asked at:Google,Amazon,Cloudflare
3

Design Pastebin

Easy
Object Storage
Expiration
Access Control
Asked at:Amazon,Google
4

Design a Unique ID Generator

Medium
Snowflake
UUID
Coordination
Clock Skew
Asked at:Twitter,Amazon,Google

AI / ML Systems

10 questions
1

Design a Model Serving Platform (like OpenAI API)

Hard
Load balancing across GPU clusters
Request queuing and rate limiting
Multi-model routing and versioning
Latency optimization and caching
Asked at:OpenAI,Anthropic
2

Design a Fine-Tuning Pipeline

Hard
Dataset ingestion and validation
Distributed training orchestration
Checkpoint management and versioning
Evaluation and automated quality checks
Asked at:OpenAI
3

Design a Real-Time Chat System (like ChatGPT)

Hard
Streaming token generation
Conversation state management
Multi-turn context handling at scale
Content filtering and safety layers
Asked at:OpenAI,Anthropic
4

Design a Distributed Training System

Hard
Data parallelism vs model parallelism
GPU cluster scheduling and fault tolerance
Gradient synchronization strategies
Checkpointing and recovery
Asked at:OpenAI,Anthropic
5

Design an AI Evaluation & Testing Harness

Hard
Benchmark suite management
Automated regression detection
Human evaluation workflow
Statistical significance testing at scale
Asked at:OpenAI
6

Design Claude's Prompt Playground

Hard
Real-time streaming token generation
Global scaling and low-latency inference
Safety content filtering layers
Multi-model version management
Asked at:Anthropic
7

Design an Inference Batching System

Hard
Dynamic batch sizing for GPU utilization
Latency SLA management
Priority queuing for different tiers
Graceful handling of 100x traffic spikes
Asked at:Anthropic,OpenAI
8

Design a Conversation Safety System

Hard
Real-time content classification pipeline
Constitutional AI enforcement layers
Escalation and human review workflow
False positive/negative trade-off management
Asked at:Anthropic
9

Design a Model Evaluation Pipeline

Hard
Benchmark suite management and versioning
Automated safety evaluation (red-teaming)
A/B testing framework for model versions
Statistical significance and regression detection
Asked at:Anthropic,OpenAI
10

Design a Distributed Training Platform

Hard
Data and model parallelism strategies
Checkpoint management and fault recovery
GPU cluster scheduling and utilization
GDPR-compliant training data handling
Asked at:Anthropic

Quick Reference: Key Concepts

SQL vs NoSQL

  • • SQL: ACID, joins, structured data
  • • NoSQL: Scale, flexibility, eventual consistency
  • • Examples: PostgreSQL vs MongoDB vs DynamoDB

CAP Theorem

  • • Consistency: All nodes see same data
  • • Availability: System always responds
  • • Partition Tolerance: Works despite network splits

Caching Strategies

  • • Cache-aside: App manages cache
  • • Write-through: Write to cache + DB
  • • Write-back: Write to cache, async to DB

Load Balancing

  • • Round Robin: Rotate through servers
  • • Least Connections: Route to least busy
  • • Consistent Hashing: Sticky sessions

Sharding Strategies

  • • Hash-based: Distribute by hash(key)
  • • Range-based: Partition by ranges
  • • Directory-based: Lookup table for mapping

Message Queues

  • • Kafka: High throughput, log-based
  • • RabbitMQ: Traditional message broker
  • • SQS: Managed, serverless option

How to Approach System Design Interview Questions

What to Expect in a System Design Interview

System design interviews are typically 45-60 minutes long and given to candidates interviewing for mid-level to senior engineering positions (SDE II and above at most companies). You will be asked to design a large-scale distributed system like Design Twitter or Design Uber from scratch.

Unlike coding interviews where there is a correct answer, system design interviews are open-ended. Interviewers evaluate your ability to gather requirements, make trade-offs, communicate clearly, and demonstrate breadth and depth of technical knowledge. The goal is not to build a production-ready system, but to show how you think about complex problems.

System Design Interview Structure

  • Requirements gathering (5-10 min): Clarify functional requirements (features) and non-functional requirements (scale, latency, availability).
  • High-level design (15-20 min): Draw the major components and data flow. Include clients, load balancers, web servers, databases, caches, and message queues as needed.
  • Deep dive (15-20 min): The interviewer will ask you to go deeper into 1-2 components. Be ready to discuss database schema, API design, caching strategy, or scaling approach in detail.
  • Trade-offs and wrap-up (5-10 min): Discuss bottlenecks, failure scenarios, and how you would evolve the system over time.

Most Frequently Asked Questions by Company

Different companies have different favorite system design questions based on their products:

  • Google: Design Google Maps, YouTube, Google Docs, Web Crawler, Typeahead
  • Meta: Design Facebook News Feed, Instagram, Messenger, WhatsApp
  • Amazon: Design Amazon e-commerce, Inventory System, Rate Limiter, S3
  • Netflix: Design Netflix streaming, Recommendation System, CDN
  • Uber: Design Uber/Lyft, Surge Pricing, Real-time Location Tracking
  • Twitter/X: Design Twitter Timeline, Trends, Search

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