When we last visited WhatsApp they’d just been acquired by Facebook for $19 billion. …
It’s always the language, the database, the network, and alike the ones challenging scalability, but never the operating system!
Unix/Linux operating systems deserve to be recognized as one of the best pieces of software ever made.
"In-memory Mnesia database using about 2TB of RAM sharded across 16 partitions to store about 18 billion records."
"Erlang love. Great language to support so many users with so few engineers"
"Asynchronicity to minimize impact of latency on throughput"
"Nodes are run in pairs. One is primary and the other secondary. If one or the other goes down they they will be handling primary and secondary traffic"
"Added a write-back cache so messages could be delivered before they had to be written to the filesystem. 98% cache hit rate"
See on highscalability.com