Redis matters because data mistakes are expensive because they affect user records, billing state, analytics, and production migrations. It gives builders a precise word for the thing they are changing, debugging, reviewing, or shipping.
ELI5
Think of Redis as a labeled drawer or rule for keeping app information organized. It gives one small job a clear name so the whole app is easier to understand.
In practice
Use it before changing storage, writing a migration, debugging stale data, or asking an agent to create a new model. In practice, name the owner, input, output, failure mode, and proof before relying on Redis.