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Redis Introduction

Stands for remote Dictionary Server.
• It is a in-memory key-value pair data store.
• It is used as a database, cache, message broker and queue.

How Redis works?

  • Redis store data in-memory and not on HDDs/SSDs.
  • Thus seek time delays are eliminated in redis.
  • Redis has variety of data structures.
    • Redis supports Replication and persistence hence very fast read operations.

Redis use cases

  • Caching
    • Database queries, persistent session, web page, images, metadata etc all can be cached.
    • Data access latency is reduced.
    • Throughput is increased.
    • And database will have less load.
  • Chat, messaging, and queues
    • Supports publisher/subscriber model with pattern matching and number of data structures.
  • Session store
  • Rich media streaming
  • Machine Learning

Redis Language support

  • Python
  • Java
  • PHP
  • Perl
  • Go
  • Ruby
  • C/C#/C++
  • JavaScript
  • js

Redis Data structure

  • String
  • Set
  • Lists
  • Sorted Lists
  • Hashes

Redis architechture

Memory optimization and architecture

  • Using 32 bit instance
    • As here the pointers are small hence less memory will be utilized but also only 2^32=4GB of memory will be referenced only.
  • Bit and byte level operations
    • With redis 2.0 new bit and byte level operations were GETRANGESETRANGEGETBIT and SETBIT. Now string can be treated as character array.
  • Use hashes when possible
    • Hashes require little space hence should be used. Suppose if object has different fields inside then instead use hashes.

Advantages of Redis

  • Redis stores data as key value and allow 512MB size for key as well as values.
  • Redis follows master slave architecture and allow data replication.
  • Redis can allow uninterrupted service and overcome failures.
  • Radis has support for various different languages.
  • Radis supports publisher subscriber messaging model.
  • Radis support transaction hence multiple commands will be queued instead of running one at a time.
  • Redis is having very low latency for read operations.
  • Redis operations are atomic i.e. latest value is used.
  • Redis has different type of data structures.

Disadvantages of Redis

  • We have to limit our data because everything is on main memory.
  • Since Data is sharded based on the hash-slots assigned to each Master. If Master holding some slots is down, data to be written to that slot will be lost.
  • Clients connecting to the Redis cluster are aware of the cluster topology, causing overhead configuration on Clients.

Redis and other databases(vs mongodb)

Redis vs Memcached

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