Redis interview questions and Answers

Redis stands for REmote DIctionary Server. Redis is an open-source in-memory database which stores the data in the key-value pairs.

For example:- NAME = Ram, here NAME is the key and Ram is the value. In-memory database means that the data is stored in the memory, but the data can also be stored in the disk.

Benefits of Redis

• in-memory database, therefore, it is swift.
• Uses the data structure to store the data
• Supports data replication
• Can be used as a cache system as well as the database.

• Data read, and Data write done by commands
• Redis is simple to configure, learn and implement.
• Redis allows data replication
• Redis works on the Client-Server mechanism.
• In Redis, there is no requirement of tables, rows, and columns.
• Redis includes pipelining that means multiple commands can be clustered and send them at once.
• Redis can be used as a database
• Redis has the master-slave feature

The latest version of Redis is 5.0.3 which got released on 12th December 2018.

Redis can be installed on the Ubuntu machines by using the command:-

sudo apt-get install Redis-server

If the user wants Redis to be installed as an object cache for Wordpress or any other PHP, then the following command can be used:-

sudo apt-get install php-redis

If the user wants to configure the Redis as a cache, /etc/Redis/redis.conf file needs to be updated, and the text editor nano can be used for this purpose.

sudo nano /etc/redis/redis.conf

Any text editor can be used.

Here is one of the way of installing the Redis on Windows:-

Architecture

1.Install some packages

• $ sudo apt-get install build-essential
• $ sudo apt-get install tcl8.5

2. Download the source code of the latest version of Redis.

• http://download.redis.io/releases/redis-5.0.3.tar.gz

3. Extract the file that has been downloaded.

4.Compile the Redis source

• $ sudo make distclean
• $ sudo make –j

5.Test the compiled files ((optional))

• $ sudo make test -j

6. After compilation, copy the Redis binaries under /usr/local/bin/ and then install the Redis server by the following instructions:-

• $ sudo make install -j
• $ cd utils
• $ sudo ./install_server.sh

7. Installation Completed

Point to be noted:- Go through this Q&A very thoroughly as this is one of the vital Redis interview questions.

• DEL:-if the key exists then it deletes the key

              Syntax:- redis 127.0.0.1:6379> DEL KEY_NAME

• EXISTS:-this checks whether the key exists or not

              Syntax:- redis 127.0.0.1:6379> EXISTS KEY_NAME

• EXPIRE:- this sets the expiry date of the key after the specified time

              Syntax:- redis 127.0.0.1:6379> Expire KEY_NAME TIME_IN_SECONDS

• TTL:-this shows the time remaining in the keys expiry

• RANDOMKEY:-this returns the random key

              Syntax:- redis 127.0.0.1:6379> RANDOMKEY

• TYPE:-this return the data type of the value which is stored in the key

• KEYS pattern:- this return the keys which match with the mentioned pattern

Following are the Redis data types:-

1. Strings:-

2. Hashes:- They represent the objects.

3. Lists:-they are the set of lines that are sorted according to the insertion order Syntax:-

4. Sets:- It is a collection of the string arranged randomly

5. Sorted Sets:-similar like the sets but here with each member, there is a score which may get repeated while the members will be unique

This particular Redis interview question explains Redis data types.