System Design Practice

1 Process

• Be clear about functional (api) and non-function (quality) requirements.
• Core entities
• API or interface
• Data flow
• High-level design
• Deep dives

2 Examples

Topic	Description	Design
Youtube	100MB DAU Support large size vedio uploading Availabitiy >> Consitency Low latency streaming Scalibility Core entities Vedio Vedio metadata User API POST /vedios {Vedio, VedioMetadata} GET /vedios/:veidoId
Whatsapp	Functional requirements group chats send / receive messages send / receive media access messages after being offline audio / vedio calling   Non-functional requirements low latency < 500ms guarantee delivery billions of users fault-tolerant Core engities user chat  message client Command sent createChat sendMessage createAttachment modifyParticipants Command received newMessage chatUpdate
Ad click Aggregator	Non-functional requirements idempotency of ad clicks (userId +  sessionAdId + Redis)
User	Functional requirements Users should input a start location and a destination request a ride Drivers should be able to accept / deny a request Non-Functional requirements Low-latency Consistency 1-1 match Highly available handle high throughput Core entities Driver Ride Rider Location	Consistency: Redis lock Location: Geohash Peak hours: Queue.