Instagram run on Amazon AWS, though Facebook finally moved Instagram to their own datacenters (as of June 2014) where FB use SSL hardware cards (cheaper than CPU and ELB for SSL on AWS).

We also terminate our SSL at the ELB level, which lessens the CPU load on nginx. -- http://instagram-engineering.tumblr.com/post/13649370142/wha...

http://www.zdnet.com/instagram-finally-picked-up-and-moved-f...

http://instagram-engineering.tumblr.com/post/89992572022/mig...