Redis - Lists, Sets and HashMaps

This is a continuation to the previous blogpost

There are 3 other data types available apart from key-value pairs

Lists

This data structure resembles the list in Python or the array in Javascript or C#. They can be used to keep recently used items. The common operations are;

Sets

A data structure that only has unique items. similar to sets in Python and Sets in Javascript and HashSets in C#. Common operations include;

Hashmaps

An hashmap is a group of key value pairs. An hashmap however cannot be nested. Lets take a case scenario of a person with a name, email and phone number

HSET person name "Joe" # Adds the key-value pair {name : joe} to the hashmap
HSET person email "[email protected]" # Adds the key-value pair {email : [email protected]} to the hashmap
HSET person phone_number " 2345656655413" # Adds the key-value pair {number : ....} to the hashmap

the HGET command can be used to get the value of a particular key in a hashmap

HGET person name # returns "Joe"

the HGETALL command all the key-value pair in the hashmap

HGETALL person 

1) "name"
2) "Joe"
3) "email"
4) "[email protected]"
5) "phone_number"
6) " 2345656655413"

the HDEL command deletes a key-value pair by its key

HDEL person name # removes {name : joe}

the HEXISTS command checks if a key exists in a hashset

HEXISTS person name # returns 0 because we've deleted it before

Those are most of the basic commands a developer is required to know.

Common Interview Questions

1. What is the full meaning of Redis?: Redis stands for REmote DIctionary Server

2. How does redis differ from traditional databases like MySQL?: Redis operates in main memory and have basic operations for accessing values quickly unlike SQL which resides on disk and has a wide range of crud operations

3. What are the limitations of Redis regarding data size and type?: Redis is designed to hold values that fits into the machines memory. It is not suitable for complex relational models with joins or for structuring large blobs

4. How do you handle caching in a distributed environment using Redis?: Handle caching by setting up redis instances as a caching layer in front of the database. using consistent hashing to distribute keys accreoss the cache nodes ensueres even load distribution and reduces cache misses

5. When should you use List data types in Redis?: Lists are great for durable atomic queues, for job queue, logs, buffers and many other use cases