I’m not sure what you mean by unique indexes. So, my guess is that you’re asking about enforcing single edge nodes? That’s not built yet.
With v0.9, we really want to push v1.0 out the door, so depending on how well it goes, we might release v1.0 in a month or so, and push all feature requests to after v1.0 release.
I’m really glad that you liked it. You can thank @pawan who found a good way to integrate transaction metadata into the HTTP endpoints 
.