[thu2111]

Don't know why this post was voted down. I used to work on Gmail, which uses a totally proprietary storage and database stack, like everything else at Google.

One of the most insightful design docs I ever read was an exploration by an engineer of how GMail 1.0 could have been implemented with commodity tech and how it'd compare cost wise. The rather sobering conclusion was that it'd have similar functionality and been cheaper to develop/run.