[johannes1234321]

> My experiences are with a pretty old mysql version (5.5, iirc), but that version allowed inserts without supplying a value to a column that is NOT NULL and has no default value.

With recent MySQL:

create table ttt (col int not null); insert into ttt () values(); ERROR: 1364: Field 'col' doesn't have a default value

> Postgres has, in addition, indexes over expression, which allows you to build indexes for specific queries into JSONB.

MySQL has that, too. I consider this quite useful, especially since MySQL also supports indexing an array of values from a JSON document. (Given `{"colors": ["red", "green", "blue" ]}` a search for `JSON_CONTAINS('$.colors', 'red')` benefits from the index.