The new stuff can be divided into a few different categories: security, performance, ease-of-use, and even some entirely new functionality.
Redis 6 brings news security features
Perhaps the biggest, most game-changing feature of Redis 6 are access control lists (ACLs). ACLs bring the concept of “users” to Redis. Each user can have a defined set of capabilities that dictate which commands they can run and on what keys.
In addition to ACLs, Redis 6 brings the ability to encrypt traffic over SSL.
Redis 6 is faster
By delegating the time spent reading and writing to I/O sockets over to other threads, the Redis process can devote more cycles to manipulating, storing, and retrieving data—boosting overall performance.Similarly, Redis’ single-threaded DEL command can now be configured to behave like the multi-thread UNLINK command that has been available since Redis version 4. Redis 6 adds a new technique for sophisticated client libraries to implement a client-side caching layer to store a subset of data in your own process.
Redis 6 is easier to use
Redis protocol（RESP3）
The expiration cycle has been rewritten in Redis 6.0 to allow for much faster expirations that more closely match the time-to-live (TTL) property. Additionally, you can now tune expirations to zero in on the accuracy required for your particular situation.
Meet the longest common subsequence family
The longest common subsequence (LCS) commands can be used to find non-contiguous sequences among strings
STRALGO LCS STRINGS salvatore sanfilippo
"salo"
How did this command come up with that result?
salvatore sanfilippo
Salvatore has mentioned the possibilities of using it for RNA and DNA analysis.
diving into redis 6.0：https://redislabs.com/blog/diving-into-redis-6/