Hi, there..
I've once hired to clone the functional of pinterest,
the buyer was from bangladesh, He has full license to sell it again and do some modification.
I can send you the demo of my past work if you interested, I'll upload it on my server.
Based on my test last january, it's stable to handle 1M fake users with a VPS(2Ghz CPU, 4GB RAM).
Looking forward for your response. Thank you.