Error: crossslot keys in request don't hash to the same slot

What's Causing This Error

The crossslot keys in request don't hash to the same slot error occurs when you try to perform an operation that involves multiple keys in a Redis Cluster, but those keys do not belong to the same hash slot. Redis Cluster distributes data across several nodes using hash slots. When an operation requires multiple keys, all the involved keys must map to the same hash slot for the operation to be executed atomically and consistently. This error message indicates that some of the keys in your request are mapped to different hash slots, which is preventing the operation from being executed.

Solution - Here's How To Resolve It

To resolve this error, you can follow these steps:

1. Use the {...} key tags: If your operation needs to involve multiple keys, you can enforce them to be hashed to the same slot by using the same prefix within curly braces ({...}) in the key names. For instance, if you have keys like user:{123}:username and user:{123}:email, both will be guaranteed to be on the same hash slot because the content inside the curly braces is identical.
2. Reconsider your data model: Optimize your data model to minimize the need for multi-key operations, as they can be difficult to maintain in a Redis Cluster environment. For instance, consider using Redis data structures such as hashes, lists, or sets to store related data together, minimizing the need for cross-slot operations.
3. Use a single-node configuration: If your use case does not require the scalability provided by a Redis Cluster, you can switch to a single-node configuration where all keys are available in the same node, thereby eliminating the possibility of encountering this error.