Redis vs Varnish: What are the differences?

Redis: An in-memory database that persists on disk. Redis is an open source, BSD licensed, advanced key-value store. It is often referred to as a data structure server since keys can contain strings, hashes, lists, sets and sorted sets; Varnish: High-performance HTTP accelerator. Varnish Cache is a web application accelerator also known as a caching HTTP reverse proxy. You install it in front of any server that speaks HTTP and configure it to cache the contents. Varnish Cache is really, really fast. It typically speeds up delivery with a factor of 300 - 1000x, depending on your architecture.

Redis can be classified as a tool in the "In-Memory Databases" category, while Varnish is grouped under "Web Cache".

"Performance", "Super fast" and "Ease of use " are the key factors why developers consider Redis; whereas "High-performance", "Very Fast" and "Very Stable" are the primary reasons why Varnish is favored.

Redis and Varnish are both open source tools. It seems that Redis with 37.4K GitHub stars and 14.4K forks on GitHub has more adoption than Varnish with 908 GitHub stars and 216 GitHub forks.

According to the StackShare community, Redis has a broader approval, being mentioned in 3265 company stacks & 1789 developers stacks; compared to Varnish, which is listed in 1006 company stacks and 140 developer stacks.