Index survives past FLUSHDB - this will be undesirable.

Consider this:

$ launchctl start io.redis.redis-server
$ redis-cli
> keys *
(empty list or set)
> json.set user1 $ '{"last":"Joe", "first":"Mc"}' INDEX person
OK
> json.index add person last $.last
OK
> JSON.QGET person Jo*
"{\"user1\":[{\"last\":\"Joe\",\"first\":\"Mc\"}]}"
> flushdb
OK
> JSON.QGET person Jo*
"{\"user1\":[]}"

This will be a very unexpected outcome for most Redis users. FLUSHDB (or FLUSHALL) should remove all data and this type of behaviour could reveal information that could be sensitive.

I assume that the indexes are behind held outside of keyspace, which I get to some degree, but this will be very strange to explain.