System Design → AWS Service Mapping Cheatsheet

Not a case-study library — that's Architecture/CaseStudies (unresolved), which covers real companies' actual production writeups. This is a study aid: 10 familiar consumer products, sketched as a generic component flow, with each component mapped to the AWS service that would implement it — useful for pattern-matching SAA-C03 question scenarios ("design a photo-sharing app...") back to the right service.

01. Design WhatsApp

Focus: Messaging system with real-time communication.

Users → Load Balancer (API Gateway) → Message Service → Message Store (Cassandra) Message Service → Cache (Redis) → Real-time Delivery (WebSocket) → back to Message Store

AWS mapping: ALB/API Gateway, ECS/Lambda for Message Service, DynamoDB or Keyspaces (Cassandra-compatible) for Message Store, ElastiCache (Redis) for Cache, API Gateway WebSocket APIs for real-time delivery.

02. Design YouTube

Focus: Video uploading, processing, and streaming.

Users → Upload Service → Raw Video (S3) → Video Processing (Transcode) → CDN (CloudFront) → Viewers Video Processing → Metadata Store (DynamoDB)

AWS mapping: S3 for raw/processed video storage, MediaConvert/Elastic Transcoder for transcoding, DynamoDB for metadata, CloudFront for delivery.

03. Design Uber

Focus: Ride matching, GPS tracking, and dispatch.

Users → API Gateway → Matching Service → Driver Service → GPS Tracking Service Matching Service → Metadata Store (DynamoDB) GPS Tracking Service → Trip Store (PostgreSQL)

AWS mapping: API Gateway, ECS/Lambda for matching/driver services, DynamoDB for metadata, RDS/Aurora PostgreSQL for trip data, IoT Core or Kinesis for GPS stream ingestion.

04. Design Netflix

Focus: Video streaming and recommendation engine.

Users → API → Streaming Service → CDN (CloudFront) → TV/Mobile Clients Streaming Service → Video Store (S3) CDN → Recommendation Engine

AWS mapping: API Gateway, S3 for video store, CloudFront for CDN, SageMaker/Personalize for the recommendation engine.

05. Design Amazon

Focus: E-commerce platform and order processing.

Users → Web/Mobile (SPA) → Order Service → Payment Service → Inventory Service Order Service → Order DB (MySQL) Inventory Service → Product DB (DynamoDB)

AWS mapping: RDS/Aurora MySQL for Order DB, DynamoDB for Product DB, Lambda/ECS microservices for Order/Payment/Inventory, EventBridge/SQS for order events.

06. Design Instagram

Focus: Photo sharing, feed generation, and stories.

Users → API Gateway → Photo/Video Service → Media Store (S3) → CDN (CloudFront) Photo/Video Service → Metadata Store (PostgreSQL) Media Store → Feed Cache (Redis) → Feed Viewers

AWS mapping: S3 for media, RDS/Aurora PostgreSQL for metadata, ElastiCache (Redis) for feed cache, CloudFront for delivery.

07. Design X (Twitter)

Focus: News feed, timelines, and tweet delivery.

Users → API Gateway → Tweet Service → Tweet Store (Cassandra) → Fanout Service Tweet Service → Search (Elasticsearch) Fanout Service → Timeline Store (Redis)

AWS mapping: DynamoDB/Keyspaces for Tweet Store, OpenSearch Service for search, ElastiCache (Redis) for timeline store, Lambda/ECS for fanout logic.

08. Design Google Drive

Focus: Cloud storage, file sync, and sharing.

Users → Sync Service → File Store (S3) → Share Service (IAM) → Shared Users File Store → Metadata Store (DynamoDB) → (feeds back into Share Service)

AWS mapping: S3 for file storage with versioning, IAM policies/pre-signed URLs for sharing, DynamoDB for file metadata, S3 Event Notifications for sync triggers.

09. Design Spotify

Focus: Music streaming and personalized recommendations.

Users → API Gateway → Streaming Service → CDN (CloudFront) → Clients Streaming Service → Audio Store (S3) Clients → Recommendation Engine

AWS mapping: S3 for audio store, CloudFront for streaming delivery, Personalize/SageMaker for recommendations.

10. Design Zoom

Focus: Video conferencing, screen sharing, and chat.

Users → Signaling Service → Video/Audio Service (WebRTC) → Chat Service → Recording Service (S3) Signaling Service → STUN/TURN Service Chat Service → Message Store (Cassandra)

AWS mapping: Kinesis Video Streams or a WebRTC media server on EC2/ECS, S3 for recordings, DynamoDB/Keyspaces for chat message store.

Key System Design Skills Covered

Scalability, High Availability, Load Balancing, Caching (Redis), Database Sharding, Replication, Microservices, CDN, Event-Driven Architecture, Message Queues (Kafka/RabbitMQ), API Gateway, WebSockets, Rate Limiting, Consistent Hashing, CAP Theorem, Distributed Systems, Fault Tolerance, Monitoring & Observability, Cloud Architecture.

Notes for SAA-C03 Study

These patterns are a good cross-check against exam domains:

• Caching & performance: ElastiCache, CloudFront — recurring across nearly every case study (WhatsApp, YouTube, Instagram, Twitter, Netflix, Spotify).
• Storage choice: S3 for blobs/media, DynamoDB for high-scale key-value metadata, RDS/Aurora for relational/transactional data (Uber trips, Amazon orders, Instagram metadata).
• Real-time delivery: WebSockets and WebRTC patterns (WhatsApp, Zoom) map to API Gateway WebSocket APIs and Kinesis Video Streams.
• Fanout/feed generation: Twitter and Instagram both illustrate push (fanout-on-write) vs. pull (fanout-on-read) trade-offs relevant to the "design for scale" exam domain.