[mathnmusic]

I built a Rails app with exactly that set up: sharding, dynamic switching of read/write queries across multiple slaves 10 years ago. It wasn't hard at all. Ruby's full dynamic nature makes many things easy.

[viraptor]

Yes, I mentioned it too https://news.ycombinator.com/item?id=24937220 - it's relatively easy to add this if needed. But I would not describe it as supported natively.