The issue is absolutely not the overhead of schemas or managing them. The issue is the overhead of systems administration when clustering. Clustering is a requ

The issue is absolutely not the overhead of schemas or managing them. The issue is the overhead of systems administration when clustering. Clustering is a requirement to support high availability, and Postgres clustering is a real bear to set up. Mongo clustering is easy. Postgres and most other SQL databases hail from the era when things ran on a "box." They're designed that way. Clustering is a bolt-on. It's that more than queries or schemas that drive NoSQL. It would have been better to fork Postgres and create a cleaned-up easy to cluster version minus the obnoxious arcana, but that's no fun. It's more fun to reinvent the wheel. Edit: We migrated from Postgres to RethinkDB for this reason and are mostly happy with it. We miss the data integrity guards of SQL but getting clustering without a full time DBA and Raft consensus fail-over without intervention is a worthy trade off. We still use Postgres for back-end warehousing and analytics but those are not live systems so they can live on a "box."