I would be interested to know what you mean by "real data store", and what you believe Facebook does badly at in terms of handling data and caching and how it could be improved.

(I am an engineer/developer/whatever at Facebook, and I'm always interested in hearing the perception of the company's technology from the community.)

I have two questions:

1. I've always been under the impression that for what Facebook does, a traditional RDBMS simply cannot handle the scale (like, not even close). Is this correct?

2. I'm also under the impression that due to the architecture Facebook runs on, from time to time some lesser-important data (ie: a status update or comment) can be lost (temporarily or permanently) and this is not considered unacceptable. (It seems perfectly reasonable to me for this particular use case.)

Perhaps it is best for the database team to talk about that themselves - wouldn't want to put words in their mouths. They gave a Tech Talk in December last year, which you can see at http://livestre.am/1aeeW

With respect to #1, I believe they use a heavily sharded MySQL cluster for at least part of their work. But I also believe you're right about #2.