[richo]

To be blunt, the simple problems are hard.

Concurrency. Locking. Cache invalidation. CAP Theorem for determining truth in distributed datasets. Feel free to solve any of them.

For the record, "I could do it if I had the time". Do it. It'll be awesome.

Reinventing the wheel is a great excercise, as long as you accept that your wheel will probably be inferior to the existing one. Or maybe it won't and it'll be the next big thing.

TL;DR, go write some code.