query limitations, data structures and Redis' way to store data in memory

strings

use cases: storing objects (complex or not) and counters

hashes

hash suits for structed objects hash implemention

sets

in op is O(1)?

use cases: Sets are great for tagging or tracking any other properties of a value for which duplicates don't make any sense (or where we want to apply set operations such as intersections and unions).

sorted sets

hashes are like strings but with fields, then sorted sets are like sets but with a score

use cases:

• leaderboard system
• anything you want sorted by an some integer, and be able to efficiently manipulate based on that score,

Pseudo Multi Key Queries

using hashes to make querying a little easier

References and Indexes

manage/update/delete these references manually is defficult

Round Trips and Pipelining

Transactions

Every Redis command is atomic, including the ones that do multiple things. Additionally, Redis has support for transactions when using multiple commands.

Redis is actually single-threaded, which is how every command is guaranteed to be atomic

starts multi then some commands ends with exec or discard

Expiration

commands: - EXPIRE - EXPIREAT - TTL - PERSIST - SETEX

ideal caching engine

Lua Scripting

keys with a TTL won't expire half-way through script execution

lua-time-limit defines how long a Lua script is allowed to execute before being terminated. Default is 5 seconds.

Replication

Redis replication doesn't yet provide automated failover, If the master dies, a slave needs to be manually promoted

Some commands are more expensive than others (sort for example) and offloading their execution to a slave can keep the overall system responsive to incoming queries

Backups

disable both snapshotting and the append-only file (aof) on the master and let a slave take care of this

Redis Cluster

Not only will this offer horizontal scaling, including rebalancing, but it'll also provide automated failover for high availability.

End

Redis is easy to learn

the real benefits Redis has to offer with its simplicity