> It's inability to allow you to query on arbitrary attributes/fields without creating a separate index (i.e. copy of the entire collection) is mind-boggling.

This attitude of everybody is incompetent at <Big Company>...I need to teach them, is what is mind-boggling.

Your statement misunderstands the design principles of a system like this one or others similar. It's precisely those design principles that led to not allowing to run arbitrary queries on the backend.

You are trying to optimize for the 99.9th percentiles at massive scale...