Scan the keyspace matching only our prefixed keys:
 - predis:hash
 - predis:zset
 - predis:set
Scan members of `predis:set`:
 - member:1
 - member:4
 - member:2
 - member:0
 - member:3
Scan members and ranks of `predis:zset`:
 - member:4 [rank: -4]
 - member:3 [rank: -3]
 - member:2 [rank: -2]
 - member:1 [rank: -1]
 - member:0 [rank: 0]
Scan fields and values of `predis:hash`:
 - field:0 => value:0
 - field:1 => value:1
 - field:2 => value:2
 - field:3 => value:3
 - field:4 => value:4