What is External Cache (Redis) primarily used for?

What is External Cache (Redis) primarily used for?

• A. A CDN for static assets.
• B. A write-back cache pattern.
• C. A standalone in-memory cache service shared across all application servers, reducing database load.
• D. An on-disk cache with persistence.

Answer: (C)

A centralized, in-memory cache like Redis is used as a fast, shared data store that all application servers can access. It holds hot data, results of expensive queries, and session information so repeats don’t hit the database each time, which reduces load and latency across the system. Being in memory and shared across servers, it provides ultra-fast access and consistency across instances, with options to expire data automatically and manage memory. While Redis can persist to disk and support other patterns, its primary purpose in typical architectures is to serve as a fast, shared cache that reduces database load.

A centralized, in-memory cache like Redis is used as a fast, shared data store that all application servers can access. It holds hot data, results of expensive queries, and session information so repeats don’t hit the database each time, which reduces load and latency across the system. Being in memory and shared across servers, it provides ultra-fast access and consistency across instances, with options to expire data automatically and manage memory. While Redis can persist to disk and support other patterns, its primary purpose in typical architectures is to serve as a fast, shared cache that reduces database load.