If you're using postgres, couldn't you just create an index on the field inside the JSONB column directly? What advantage are you getting from extracting it to a separate column?
CREATE INDEX idx_status_gin
ON my_table
USING gin ((data->'status'));
Yes, as far as indices go, GIN indices are very expensive especially on modification. They're worthwhile in cases where you want to do arbitrary querying on JSON data, but you definitely don't want to overuse them.
If you can get away with a regular index on either a generated column or an expression, then you absolutely should.
