One example where SQL looses is Graph databases, but (MonogoDB sucks here too ¯\_(ツ)_/¯). Otherwise PostgreSQL rules, with current hardware you can easily fit all database in RAM. If PostgreSQL not enough, there is also CockroachDB and Spanner.
I can miss some other use cases for other DBs, like BigTable and DynamoDB etc.
PostgreSQL supports document database (XML, JSON). PostgreSQL supports key/value stores.
PostgreSQL, it's Not Only SQL :p
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