It depends what you're using it for. Postgres is a very good all-around choice these days (compared to when the whole 'noSql' thing got started) and also supports document-based scenarios quite well via JSON/JSONB columns and its support for these datatypes in queries, updates, indexing etc. Sharding and replication can also be set up via fairly general mechanisms, as described in pgSQL documentation. (For instance, the FDW facility is often used to set up sharding, but it could also support e.g. aggregation.)