Top 20 Redis Interview Questions and Answers

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Redis is an open-source, in-memory data structure store known for its speed and flexibility. It was created in 2009 by Salvatore Sanfilippo (also known as antirez) to solve real-time performance issues in his startup. Over time, Redis has grown into one of the most popular tools for caching, message brokering, and real-time analytics. Its simplicity and performance make it a favorite in modern backend systems. That’s why Redis interview questions frequently appear in developer, DevOps, and data engineering interviews. In this blog, we have compiled 20 commonly asked Redis interview questions and answers to help you prepare with confidence.  

Fun Fact – Over 10,000 businesses, including giants like British Airways and Viacom18, use Redis Enterprise daily.

Basic Level Redis Interview Questions 

Here are the most asked Redis interview questions and answers to help freshers prepare easily. 

1. What is Redis and how is it different from traditional databases?

Redis is an open-source, in-memory data store. Unlike traditional databases that write to disk, Redis keeps data in RAM, making it much faster. It is often used for caching, real-time analytics, and pub/sub systems.

2. What data types are supported by Redis?

Redis supports several key data types: Strings, Lists, Sets, Sorted Sets, Hashes, Bitmaps, and HyperLogLogs. Each serves different use cases, like queues or user sessions.

3. How do you set and retrieve a key-value pair in Redis?

You use the SET command to store a value and GET to retrieve it. 

For example:

SET name “Alice”

GET name

This returns “Alice”.

4. What is the purpose of the EXPIRE command in Redis?

EXPIRE sets a time-to-live (TTL) on a key. Once the TTL ends, the key is automatically deleted. It is helpful for caching temporary data.

5. What is the difference between Redis and Memcached?

Redis supports multiple data types and persistence. Memcached only supports simple key-value pairs in memory. Redis also offers replication and scripting.

6. How does Redis handle persistence?

Redis uses two methods: RDB snapshots and AOF (Append Only File). RDB saves data at intervals. AOF logs every write operation. You can use one or both, depending on your needs.

Advanced Level Redis Interview Questions for Experienced Professionals 

Here are some commonly asked Redis interview questions and answers for experienced candidates.

7. How does Redis Cluster work and when would you use it?

Redis Cluster automatically splits data across multiple nodes using hash slots. It provides partitioning and high availability without a central node. You use it when a single Redis instance can’t handle your data or traffic.

8. What are Redis Sentinel and its main responsibilities?

Redis Sentinel monitors master and replica nodes. If the master fails, it promotes a replica to master. It also notifies clients and handles failover automatically. It is ideal for single-node setups needing high availability.

9. How can Redis handle high availability and failover?

You can set up Redis Sentinel or Redis Cluster. Sentinel is best for simpler setups with automatic failover. Redis Cluster offers both sharding and failover across multiple masters and replicas.

10. What are the trade-offs between RDB and AOF persistence in Redis?

RDB is faster for recovery and uses less disk, but may lose recent writes. AOF logs each operation and is safer but slower to load. You can combine both for balance.

11. How would you prevent cache stampede in Redis?

You can use locking, request coalescing, or add jitter to TTLs. Setting SETNX with a short lock key helps avoid multiple recomputations. Some use stale cache responses when needed.

12. What happens when Redis runs out of memory?

Redis uses a maxmemory policy. Depending on the policy, it evicts keys (like LRU or TTL-based) or returns an error. If no eviction policy is set, write operations will fail.

Redis Cache Interview Questions

13. What is cache eviction in Redis and which policies are supported?

Cache eviction happens when Redis hits the memory limit. It removes keys based on a set policy. As of 2025, Redis supports these eviction policies: noeviction, allkeys-lru, volatile-lru, allkeys-random, volatile-random, and volatile-ttl. LRU is the most used.

14. How does Redis handle cache invalidation?

Redis can remove expired keys automatically using TTL. For manual control, you can use the DEL or UNLINK command to delete keys. In some setups, cache invalidation is done through pub/sub or versioning.

15. What are the benefits of using Redis as a caching layer?

It is very fast, supports multiple data types, and works well with real-time systems. Redis reduces load on databases and speeds up API responses. It also supports TTLs and eviction, which helps manage memory.

16. How do you implement TTL for cached data in Redis?

You can set TTL using EXPIRE or directly with SET key value EX 60. This stores the key with a 60-second expiry. I often use this to store API responses that don’t change often.

Redis Cache Spring Boot Interview Questions

17. How do you integrate Redis cache in a Spring Boot application?

Add the required Redis dependencies, like spring-boot-starter-data-redis and spring-boot-starter-cache. Then annotate your main class with @EnableCaching. Spring Boot auto-configures the cache manager.

18. What annotations are used in Spring Boot for caching with Redis?

You can use @Cacheable to read from the cache, @CachePut to update it, and @CacheEvict to remove keys. These annotations work well with Redis when caching is enabled.

19. How can you configure Redis connection settings in application.properties?

You define properties like:

spring.redis.host=localhost

spring.redis.port=6379

You can also add timeout, password, and TTL settings. These properties tell Spring where to connect.

20. What happens if Redis is down – how does Spring Boot handle that in caching?

If Redis is unavailable, Spring throws runtime exceptions. To handle this, developers often use fallback logic or disable caching for critical services. You can also configure error handling in your cache config bean.

Also Read - Top 100+ Spring Boot Interview Questions

Tips to Prepare for Redis Interview 

Here are some quick and practical Redis interview tips to boost your confidence and readiness –

• Understand core Redis commands and their use cases
• Practice with real Redis CLI examples
• Know differences between Redis, Memcached, and traditional databases
• Review Redis persistence and eviction policies
• Learn how Redis handles high availability and clustering
• Read the latest Redis docs and changelogs

Wrapping Up

With these 20 Redis interview questions and answers, you are better prepared to face real interviews. Whether you are applying as a fresher or an experienced engineer – a strong understanding of Redis can set you apart.

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