How WhatsApp Scaled to Billions of Users

2 months ago

WhatsApp served 900 million users with just 50 engineers, showcasing efficiency through deliberate technical choices.
Key technologies included Erlang for concurrency, FreeBSD for networking performance, and a modified XMPP protocol for mobile efficiency.
Erlang's actor model and lightweight processes enabled handling 2+ million concurrent connections per server.
Supervisors in Erlang's architecture allowed for automatic recovery from crashes, ensuring high availability.
WhatsApp used Mnesia for fast in-memory data storage and MySQL for persistent data, optimizing performance and scalability.
FreeBSD was chosen over Linux for its superior networking stack and stability under extreme load.
End-to-end encryption was implemented using the Signal Protocol, ensuring message security and privacy.
Media handling was optimized by encrypting files on the client side and using CDNs for distribution.
Multi-device support required encrypting messages separately for each device, maintaining end-to-end encryption.
Lessons include choosing the right tools over popular ones, designing for failure, and embracing simplicity.

Hasty Briefsbeta