Is Objective C really that much better? If you have decent APIs/libraries, C++ would be just fine.
They've also open sourced their server: https://github.com/okws/okws
If Ok-Cupid were started today I highly doubt they would do that the same way. But given when they did start it I figure they literally did not have a choice.
It's still got the same C warts that C++ does in a lot of place, but it is far simpler and less leaky than C++.
C++ is still faster and more cross platform, than objective-c
--Have done both professionally