Hemanth Kumar - Get SDE Ready

High-Level Design (HLD) of WhatsApp Introduction to High-Level System Design What is System Design? Difference Between HLD and LLD Key Considerations in HLD System Design Fundamentals Functional vs. Non-Functional Requirements Scalability, Availability, and Reliability Latency and Throughput Considerations Load Balancing Strategies Architectural Patterns Monolithic vs. Microservices Architecture Layered Architecture Event-Driven Architecture Serverless Architecture Model-View-Controller (MVC) Pattern CQRS (Command Query Responsibility Segregation) Scaling Strategies Vertical Scaling vs. Horizontal Scaling Sharding and Partitioning Data Replication and Consistency Models Load Balancing Strategies CDN and Edge Computing Database Design in HLD SQL vs. NoSQL Databases CAP Theorem and its Impact on System Design Database Indexing and Query Optimization Database Sharding and Partitioning Replication Strategies API Design and Communication REST vs. GraphQL vs. gRPC Designing Scalable APIs Rate Limiting and Throttling Authentication & Authorization (OAuth, JWT) Caching Strategies Types of Caching Cache Invalidation Strategies Redis vs. Memcached Cache-Aside, Write-Through, and Write-Behind Strategies Message Queues and Event-Driven Systems Kafka vs. RabbitMQ vs. SQS Pub-Sub vs. Point-to-Point Messaging Handling Asynchronous Workloads Eventual Consistency in Distributed Systems Security in System Design Encryption (AES, RSA, TLS) API Security Best Practices Secure Data Storage and Access Control DDoS Protection and Rate Limiting Observability and Monitoring Logging Strategies (ELK Stack, Prometheus, Grafana) API Security Best Practices Secure Data Storage and Access Control DDoS Protection and Rate Limiting Real-World System Design Case Studies Distributed locking (Locking and its Types) Memory leaks and Out of memory issues HLD of YouTube HLD of WhatsApp What is System Design? Difference Between HLD and LLD Key Considerations in HLD Functional vs. Non-Functional Requirements Scalability, Availability, and Reliability Latency and Throughput Considerations Load Balancing Strategies Monolithic vs. Microservices Architecture Layered Architecture Event-Driven Architecture Serverless Architecture Model-View-Controller (MVC) Pattern CQRS (Command Query Responsibility Segregation) Vertical Scaling vs. Horizontal Scaling Sharding and Partitioning Data Replication and Consistency Models Load Balancing Strategies CDN and Edge Computing SQL vs. NoSQL Databases CAP Theorem and its Impact on System Design Database Indexing and Query Optimization Database Sharding and Partitioning Replication Strategies REST vs. GraphQL vs. gRPC Designing Scalable APIs Rate Limiting and Throttling Authentication & Authorization (OAuth, JWT) Types of Caching Cache Invalidation Strategies Redis vs. Memcached Cache-Aside, Write-Through, and Write-Behind Strategies Kafka vs. RabbitMQ vs. SQS Pub-Sub vs. Point-to-Point Messaging Handling Asynchronous Workloads Eventual Consistency in Distributed Systems Encryption (AES, RSA, TLS) API Security Best Practices Secure Data Storage and Access Control DDoS Protection and Rate Limiting Logging Strategies (ELK Stack, Prometheus, Grafana) API Security Best Practices Secure Data Storage and Access Control DDoS Protection and Rate Limiting Distributed locking (Locking and its Types) Memory leaks and Out of memory issues HLD of YouTube HLD of WhatsApp 1. About the SystemWhatsApp is a global messaging platform that facilitates real-time communication through text, images, videos, voice notes, and calls. It is designed to be:Highly Scalable: Supports billions of users.Real-Time: Messages delivered instantly.Highly Available: Minimal downtime.Secure: End-to-end encryption ensures privacy. 2. Requirements & GoalsFunctional RequirementsUser Management: Signup, login, profile updates, and contact management.Messaging: Send/receive text, images, videos, and files.Real-time Communication: Implemented using WebSockets.Group Chats: Users can create and participate in group conversations.Voice/Video Calls: Supports one-on-one and group calls.Status Updates: Users can post text, images, and videos.Notifications: Push and in-app notifications.Security: End-to-end encryption for messages and calls. Non-Functional RequirementsScalability: Supports billions of messages daily.Low Latency: Instant message delivery.High Availability: 24/7 uptime.Data Consistency: Message ordering must be maintained.Efficient Storage: Optimized storage for messages and media. 3. Capacity Estimations and ConstraintsAssumptionsDaily Active Users (DAU): 50 millionMessages per User per Day: 20Total Messages per Day: 50M × 20 = 1BMedia Messages: 5% of total messages (50M)Average Message Size: 100 bytes for text, 100 KB for mediaStorage Needs:Text: 950M × 100B = ~95GB/dayMedia: 50M × 100KB = ~5TB/dayTotal Storage per Day: ~5.1TB5-Year Projection: ~9.3PBBandwidth: ~120 MB/secRequests per Second (RPS): ~24K 4. System APIsAuthenticationPOST /api/login: Authenticate user and return session token.POST /api/logout: Logout user.MessagingPOST /api/messages: Send a message.GET /api/messages: Retrieve messages for a user.Group ChatsPOST /api/groups: Create a group.POST /api/groups/add: Add user to a group.POST /api/groups/messages: Send a group message.Voice/Video CallsPOST /api/calls/start: Start a call.POST /api/calls/end: End a call.Status UpdatesPOST /api/status: Post status update.GET /api/status: Retrieve status updates.NotificationsPOST /api/notifications: Send push notifications. 5. Data Model DesignTablesUsers: Stores user information.Messages: Stores messages with type, content, and timestamps.Chats: Represents private chats between users.Users_Chats: Maps users and chats (N:M relationship).Groups: Stores group details.Users_Groups: Maps users and groups (N:M relationship).Database ChoiceRelational Databases (PostgreSQL): For structured data (users, chats, groups).NoSQL (Cassandra, DynamoDB): For messages to ensure scalability. 6. API DesignGet All Chats or GroupsgetAll(userID: UUID): Chat[] | Group[]Get MessagesgetMessages(userID: UUID, channelID: UUID): Message[]Send MessagesendMessage(userID: UUID, channelID: UUID, message: Message): booleanJoin/Leave GroupjoinGroup(userID: UUID, channelID: UUID): booleanleaveGroup(userID: UUID, channelID: UUID): boolean 7. High-Level ArchitectureMicroservices-Based ArchitectureCore Services:User Service: Manages user authentication and profile information.Chat Service: Handles real-time messaging via WebSockets.Notification Service: Sends push notifications.Presence Service: Tracks online status.Media Service: Handles media uploads and storage.Inter-Service CommunicationREST API & gRPC for synchronous calls.Message Queue (Kafka/RabbitMQ) for asynchronous processing. 8. Scaling and Optimization StrategiesHorizontal ScalingLoad Balancers (NGINX, HAProxy) distribute traffic.Multiple database shards to handle storage efficiently.CachingRedis/Memcached for frequently accessed data (user profiles, messages).Data Storage StrategyCold Storage: Older messages archived to reduce database load.CDN: Distributes media content for reduced latency. 9. Security ConsiderationsEnd-to-End Encryption (E2EE): Ensures message confidentiality.OAuth & Token-Based Authentication: Secures API access.Rate Limiting & Throttling: Prevents spam attacks. 10. ConclusionThis HLD provides a structured approach to designing WhatsApp’s architecture, ensuring scalability, high availability, and robust security measures. Got Confusion ? Accelerate your Path to a Product based Career Boost your career or get hired at top product-based companies by joining our expertly crafted courses. Gain practical skills and real-world knowledge to help you succeed. Explore our flagship courses Reach Out Now If you have any queries, please fill out this form. We will surely reach out to you. Contact Email Reach us at the following email address. arun@getsdeready.com Phone Number You can reach us by phone as well. +91-97737 28034 Our Location Rohini, Sector-3, Delhi-110085

Author: Hemanth Kumar

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