Top Redis Cluster Interview Questions and Expert Answers

Some common Redis Cluster interview questions may look simple, but mastering them for interviews is challenging.

Q: How many slots does a Redis Cluster have?

A: 16384 slots.

Q: Does it use a consistent hashing algorithm?

A: No. It uses hash slots: each key is hashed with CRC16, the result modulo 16384 determines the slot.

Q: What are the main use cases for Redis Cluster?

A: Redis Cluster is a distributed, highly‑available in‑memory database suitable for large‑scale data, high‑concurrency reads/writes, high availability, disaster recovery, and dynamic scaling.

High‑concurrency read/write

Large data storage

High availability and disaster recovery

Dynamic scaling

Q: What are the key configuration items for Redis Cluster?

A: Enabling cluster mode, cluster state file, node timeout, log file, PID file, etc.

Q: What is a hash slot?

A: A hash slot is the core sharding mechanism that distributes data evenly across nodes, supporting dynamic scaling, failover, and easy maintenance. Advantages include data partitioning, dynamic expansion/reduction, fault tolerance, and manageability.

Q: What is a hash tag?

A: When a command involves multiple keys in different slots, it fails. By using a hash tag (the part of the key inside curly braces {}), you force those keys into the same slot. For example, hello:{star} and hello:{world} reside in the same slot.

Q: How many ports does a Redis Cluster node have?

A: Two ports: one for client communication (default 6379) and one for inter‑node communication (default client port + 10000, e.g., 16379).

Q: Is Redis Cluster strongly consistent?

A: No. It uses asynchronous replication: the master replies to the client before replicating to replicas, so data loss is possible during failures.