“Instagram scaled from 0 to 14 million users in just over a year, from October 2010 to December 2011. They did this with only 3 engineers.”
The stack was Django, Postgres, Pgbouncer, Nginx, Memcached and a pile of EC2 boxes. Nothing on the list was new or clever. The first of the three principles was to use proven, solid technologies. Boring tools are why three engineers were enough.