Summary

This article provides an extensive compilation of Redis interview questions, covering a wide range of topics from basic concepts to advanced features, aiming to prepare candidates for successful interviews.

Abstract

The article titled "87 Redis Interview Questions That Cover Everything, Never Fear Redis in Interviews Again 🤣" is a comprehensive guide designed to bolster one's understanding and expertise in Redis. It addresses various aspects of Redis, including its role as an in-memory database, its capabilities beyond caching, and the diverse data structures it supports. The content delves into the reasons behind Redis's performance, its persistence mechanisms, transactional capabilities, and strategies for performance optimization. It also explores Redis's high availability features, memory management, common production issues, and best practices for operations and maintenance. The article emphasizes the importance of understanding Redis's underlying architecture and its practical applications, ensuring that readers are well-equipped to tackle interview questions and effectively apply Redis in real-world scenarios.

Opinions

The author believes that mastering Redis interview questions is crucial for impressing potential employers and improving application performance, scalability, and reliability.
Redis is presented as a versatile tool that extends beyond simple caching, offering a variety of data structures and the ability to function as a message queue.
The article suggests that understanding the evolution of Redis, including its shift from single-threading to multi-threading in version 6.0, is important for candidates.
It emphasizes the need to be familiar with both RDB and AOF persistence methods, including their advantages, disadvantages, and the hybrid approach introduced in Redis 4.0.
The author highlights the significance of knowing how to handle common Redis production problems, such as cache breakdown, cache penetration, and cache avalanche, as well as strategies for data recovery and memory management.
The article underscores the importance of understanding Redis Sentinel and Redis Cluster for ensuring high availability and handling data sharding and replication.
It encourages readers to explore Redis's underlying data structures, such as SDS, dictionary implementation, and skip lists, to better grasp how Redis operates and performs.
The author advocates for practical knowledge of Redis applications, including implementing asynchronous queues, delay queues, and distributed locks, to demonstrate competence during interviews.
Readers are invited to engage with the content by asking questions and providing feedback, indicating the author's commitment to creating an interactive learning experience.

87 Redis Interview Questions That Cover Everything, Never Fear Redis in Interviews Again 🤣

Redis is a powerful and popular open source database that can store and process data in memory. Redis can help you improve the performance, scalability, and reliability of your applications.

But how well do you know Redis? Do you want to learn more about its features, principles, and best practices? Do you want to ace the Redis interview questions and impress your potential employers?

If you answered yes to any of these questions, then this article is for you.

In this article, I will share with you some of the most common and important Redis interview questions that cover various topics such as Redis basics, persistence, transactions, performance optimization, high availability, cluster, application, underlying structure and data structure, etc.

You can use this article as a guide map when you review your Redis knowledge, and fill in the gaps.

Redis Basics

1. What is Redis? 2. Why use Redis/Why use cache? 3. What else can Redis do besides caching? 4. Can Redis be used as a message queue? 5. What data structures does Redis have? 6. Why is Redis fast? 7. Can you explain 1/0 multiplexing? 8. Why did Redis choose single threading in the early days? 9. What’s the deal with Redis 6.0 using multithreading? 10. What are the common technical solutions for distributed caching? 11. What are the differences and similarities between Redis and Memcached? 12. How to implement distributed locks based on Redis?

Redis Persistence Mechanism

1. What are the persistence methods of Redis? What are the differences? 2. What are the advantages and disadvantages of RDB and AOF? 3. How to choose between RDB and AOF? 4. How to recover Redis data? 5. Do you know about Redis 4.0’s hybrid persistence? 6. How to ensure that Redis can recover data after restarting?

Redis Transactions

How to use Redis transactions?
Does Redis support atomicity?
How to solve the shortcomings of Redis transactions?

Redis Performance Optimization

What is a big key?
What are the dangers of big key?
How to find big key?

Redis High Availability

1. Do you know about master-slave replication? 2. What are the common topologies of Redis master-slave replication? 3. Do you know the principle of Redis master-slave replication? 4. How do you synchronize data between master and slave nodes? 5. What are the problems with master-slave replication? 6. Do you know about Redis Sentinel (Sentinel)? 7. Do you know the implementation principle of Redis Sentinel (Sentinel)? 8. Do you know about leader Sentinel node election? 9. How is the new master node selected? 10. Do you know about Redis cluster? 11. How is data partitioned in a cluster? 12. Can you explain the principle of Redis cluster? 13. How do you scale a cluster?

Redis Memory Management

What’s the use of setting expiration time for cached data in Redis?
How does Redis determine whether data has expired or not?
What are the deletion strategies for expired data?
Do you know about Redis memory eviction mechanism?

Redis Production Problems

1. What are cache breakdown, cache penetration, and cache avalanche? 2. Can you talk about Bloom filter? 3. How to ensure the consistency of cache and database data? 4. How to ensure the consistency of local cache and distributed cache? 5. How to deal with hotkey? 6. How to do cache preheating? 7. Hotkey reconstruction? Problem? Solution? 8. Bottomless pit problem? How to solve?

Redis Operation and Maintenance

1. How to deal with Redis memory shortage? 2. What are the data recovery strategies for Redis? 3. What are the memory overflow control/memory eviction strategies for Redis? 4. Redis blocking? How to solve? 5. Do you know about big key problem? 6. What are the common performance problems and solutions for Redis?

Redis Sentinel:

1.What is Sentinel? What is it used for? 2.How does Sentinel detect whether a node is offline or not? What is the difference between subjective offline and objective offline? 3.How does Sentinel implement failover? 4.Why is it recommended to deploy multiple sentinel nodes (sentinel cluster)? 5.How does Sentinel select a new master (election mechanism)? 6.How to select a leader from Sentinel cluster?

Redis Cluster:

1.Why do we need Redis Cluster? What problem does it solve? What are its advantages? 2.How does Redis Cluster perform sharding? 3.Why does Redis Cluster have 16384 hash slots? 4.How to determine which hash slot a given key should be distributed to? 5.Does Redis Cluster support reassigning hash slots? 6.Can Redis Cluster provide service during scaling up or down?

Redis Application

1. How to implement asynchronous queue using Redis? 2. How to implement delay queue using Redis? 3. Does Redis support transactions? 4. Do you know how to use Redis and Lua scripts? 5. Do you know about Redis pipeline? 6. Do you know how to implement distributed lock using Redis?

Underlying Structure and Data Structure

1. Can you talk about the underlying data structure of Redis? 2. What are the advantages of SDS over C strings in Redis? 3. How is dictionary implemented in Redis ? Do you know about Rehash ? 4. How is skip list implemented in Redis ? Principle ? 5. Do you know about compressed list ? 6. Do you know about quick list ? 7. What are the application scenarios of String ? 8. Is it better to store object data as String or Hash ? 9. What is the underlying implementation of String ? 10. Is it better to store shopping cart information as String or Hash ? 11. How to implement a ranking list using Redis ? 12. What commands do you need to use Set to implement a lottery system ? 13. How to use Bitmap to count active users ? 14. How to use Hyper Loglog to count page UV ?

I hope you enjoyed this article and learned something new about Redis.

If you have any questions, comments, or feedback, please feel free to share them in the comment section below. 💬

Good luck with your interview!