zset is a very usefull data structure, to store real world data collection, such as User List, News List, Feeds, etc. zset can be considered as a two-column table in relational database. One column is ‘key’ of UNIQUE, the other is ‘score’ of float type.
zset has one limitation, the ‘key’ column could not store very large data, it usually stores a string of no more than 100 bytes.
