WhatsApp Messaging at Scale
WhatsApp messaging architecture: Erlang concurrency, end-to-end encryption, and handling billions of messages daily.
Core Architecture
Client Apps
iOS, Android, Web, Desktop clients
End-to-end encryption, message queuing, media compression
Chat Server
Real-time message routing and delivery
Erlang/OTP for massive concurrency, XMPP protocol
Media Server
Image, video, document processing
FreeBSD servers, FFmpeg transcoding, CDN integration
Database Cluster
Message storage and user data
MySQL sharding, HBase for message history
Scale & Performance
Largest messaging platform globally
Peak traffic during holidays and events
End-to-end including encryption/decryption
Erlang concurrency model advantage
Engineering Challenges
Challenge: End-to-End Encryption at Scale
Solution: Signal Protocol implementation
Impact: Zero server-side message decryption capability
Challenge: Global Message Routing
Solution: Geographic server distribution + intelligent routing
Impact: Consistent sub-second delivery worldwide
Challenge: Media Storage Costs
Solution: Aggressive compression + auto-deletion policies
Impact: 70% reduction in storage requirements
Challenge: Spam and Abuse Prevention
Solution: ML-based detection + user reporting systems
Impact: 99.5% spam detection accuracy
Technical Innovations
Erlang for Concurrency
Actor model for message routing
Handle millions of connections per server
Each chat room as isolated Erlang process
Protocol Optimization
Custom binary protocol over TCP
50% less bandwidth than HTTP alternatives
Message headers compressed to minimal bytes
Smart Media Handling
Client-side compression + server transcoding
Fast uploads with quality preservation
Photos compressed 80% before upload
Aggressive Caching
Message routing tables in memory
Sub-second message delivery globally
User presence cached for instant status
Key System Design Lessons
Erlang for messaging systems: Actor model provides natural isolation and fault tolerance for chat applications
End-to-end encryption at scale: Signal Protocol enables privacy without server-side key management
Minimal server architecture: Push complexity to clients to reduce infrastructure costs and improve reliability
Protocol optimization: Custom binary protocols can provide significant bandwidth savings over HTTP