[isignal]

Postgres supports indexing an arbitrary json document. https://www.postgresql.org/docs/current/datatype-json.html

Not sure if the query capabilities and syntax match azure docdb but the basic functionality should be workable.

[atombender]

Of course it does, but it's limited.

GIN does not support range searches (needed for <, <=, >, >=), prefix or wildcard, etc. It also doesn't support index-only scans, last I checked. You cannot efficiently ORDER BY a nested GIN value.

I recommend reading the paper.