Top Redis Interview Questions and Answers

Here are top Redis interview questions,

1. What is Redis?

Redis is an open-source, in-memory data structure store, often referred to as a data structure server. It is commonly used as a caching layer and message broker due to its high performance and low latency.

 

2. What data structures does Redis support?

Redis supports various data structures, including strings, lists, sets, sorted sets, hashes, bitmaps, hyperloglogs, and geospatial indexes.

 

3. How do you install Redis?

The installation process depends on your operating system. For Linux-based systems, you can use package managers like `apt` or `yum`. For macOS, you can use Homebrew. For Windows, Redis can be installed using the official Windows binary.

 

4. How do you start and stop the Redis server?

To start the Redis server, use the command:

      ```

      redis-server

      ```

      To stop the Redis server, use the command:

      ```

      redis-cli shutdown

      ```

 

5. How can you set and retrieve values in Redis?

To set a value, use the `SET` command:

      ```

      SET key value

      ```

      To retrieve a value, use the `GET` command:

      ```

      GET key

      ```

 

6. What is the purpose of the expiration time in Redis?

The expiration time allows you to set a time-to-live (TTL) for a key. Once the TTL expires, the key and its value will be automatically removed from the Redis database.

 

7. How do you delete keys in Redis?

To delete a key, use the `DEL` command:

      ```

      DEL key

      ```

 

8. What is the difference between Redis strings and hashes?

Redis strings store a single value, while hashes store multiple key-value pairs.

 

9. How do you perform atomic operations in Redis?

Redis commands are atomic by default, meaning they are executed as a single isolated operation and not interrupted by other commands.

 

10. How can you perform batch operations in Redis?

You can use Redis pipelines to perform multiple commands in a batch, which reduces the round-trip time between the client and the server.

 

11. What are Redis transactions?

Redis transactions allow you to group multiple commands into a single atomic operation using the `MULTI`, `EXEC`, and `DISCARD` commands.

 

12. How do you implement pub-sub in Redis?

Redis supports Publish/Subscribe (pub-sub) messaging using the `PUBLISH`, `SUBSCRIBE`, and `UNSUBSCRIBE` commands to send and receive messages to multiple clients.

 

13. What are Redis lists and sets used for?

Redis lists are used to store ordered collections of strings, while sets are used to store unordered collections of unique strings.

 

14. How do you implement sorted sets in Redis?

Sorted sets in Redis are implemented using the `ZADD`, `ZRANGE`, and `ZREVRANGE` commands, allowing you to store elements with associated scores and perform range-based queries.

 

15. What is Redis replication?

Redis replication is a feature that allows Redis to create a copy of the master instance and sync data to one or more slave instances for high availability and data redundancy.

 

16. How do you enable authentication in Redis?

To enable authentication, set the `requirepass` directive in the Redis configuration file and provide the password in the client connection.

 

17. What is the purpose of Redis snapshots (RDB files) and append-only files (AOF)?

Redis snapshots (RDB files) are used to persist data to disk at specified intervals for data backup and recovery. Append-only files (AOF) log every write operation, providing an alternative method of persistence.

 

18. How can you monitor Redis performance and operations?

Redis provides several commands like `INFO`, `MONITOR`, and `slowlog` to monitor performance metrics and track slow commands.

 

19. What are Lua scripts in Redis, and how are they used?

Redis supports Lua scripting, allowing you to execute complex operations atomically and reduce round-trip overhead between the client and server.

 

20. What are Redis clusters, and how do they work?

Redis clusters are a way to distribute data across multiple Redis instances for horizontal scaling and improved performance. The data is sharded across nodes using a consistent hashing algorithm.

 

Above are few top Redis interview questions. Remember to prepare and expand on these answers.

Good luck with your interview!  👍