Technology Explained — Hey There! I am using WhatsApp

Sender Receiver Scenarios in WhatsApp

  • When sender A is online , but not the receiver B. The message will be stored in a database by the server, waiting B to be online.
  • When sender A sends a Whatsapp but he is not connected to Internet. Then what? Message is stored in A’s local storage and sent to server once online.
  • When both A and B are online. That’s great. NO database or local storage need. Msg from A to server , and then to B.

Last Seen/Online - How does that work?

What about storing heavy Images and Videos??

More Technical — Sent, Delievered, Seen

Tech Behind the Messaging App

  • Progaramming language- Erlang . It’s super fast, support for lightweight threads to handle 200 million connections.
  • Operationg System — FreeBSD. It is open source!
  • Database — AMNESIA. A handy key-value storage.
  • Web Server --YAWS(Yet Another Web Server)



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Aayush Agarwal

Aayush Agarwal


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