I also don't know, but anyone making a relay implementation very easily = basically implies using an existing database (of which SQL is probably a majority).

The person who creates their own indices manually is an expert, and they probably should be using a proven product instead of fiddling around, no? 

Maybe we should define "ultra-flexible" but having a powerful querying language encourages bad behaviors in developers...why? what do you mean by that? 

Limited querying language is wasteful because we need to make multiple queries vs one, download tonnes of events when a few would suffice, make client side operations that should not happen, etc