Design WhatsApp for 100 Million Users System Design & Capacity Planning

How would you design a WhatsApp-like messaging system capable of supporting 100 million daily active users? In this video, I walk through a complete system design and capacity planning exercise, covering workload assumptions, traffic calculations, infrastructure sizing, and a scalable architecture. We will break down the problem step by step, from defining functional and non-functional requirements to estimating read/write throughput, storage, bandwidth, database capacity, CDN requirements, and backups. 📌 Topics Covered ✅ Functional Requirements (FRs) ✅ Non-Functional Requirements (NFRs) ✅ Workload assumptions and DAU estimation ✅ Daily message and request volume ✅ Read RPS, Write RPS, and Peak RPS calculations ✅ Message and media storage estimation ✅ Network bandwidth estimation ✅ Database sharding, caching, and replication ✅ CDN architecture and media delivery ✅ Backup strategy and disaster recovery ✅ High-level system architecture ✅ Horizontal scaling and future growth estimation ✅ AI-assisted validation of capacity-planning assumptions 🏗️ Key Design Concepts Horizontal scaling and load balancing Distributed messaging and asynchronous processing Message persistence and delivery acknowledgements Distributed caching and database partitioning Object storage and content delivery networks High availability, durability, and fault tolerance Monitoring, observability, and disaster recovery 🎯 Who Should Watch? This walkthrough is useful for: Software engineers preparing for system design interviews Backend developers and DevOps engineers Cloud and infrastructure engineers Students learning distributed systems and capacity planning Anyone interested in designing large-scale messaging platforms ⚠️ Important Note The calculations in this video use illustrative workload assumptions for a hypothetical system targeting 100 million daily active users. They are not official WhatsApp infrastructure statistics. Actual capacity requirements depend on real traffic patterns, message sizes, group fan-out, retention policies, caching efficiency, and availability requirements. 🔖 Hashtags #SystemDesign #WhatsApp #CapacityPlanning #SystemDesignInterview #DistributedSystems #Scalability #BackendEngineering #SoftwareArchitecture #CloudComputing #TechLearning   / rishab-raj-   https://github.com/RishOpss