caching - Redis cache vs using memory directly

Question

I have not used Redis yet, but I heard about it and plan to try it as cache storing.

I heard Redis using memory as cache store database, so what's the difference if I use a variable as an object or dictionary datatype to store data? like:

var cache = {
    key: {

    },
    key: {

    }
    ...
}

What's the advantage Redis have?

Answer 1

Redis is a remote data structure server. It is certainly slower than just storing the data in local memory (since it involves socket roundtrips to fetch/store the data). However, it also brings some interesting properties:

• Redis can be accessed by all the processes of your applications, possibly running on several nodes (something local memory cannot achieve).

• Redis memory storage is quite efficient, and done in a separate process. If the application runs on a platform whose memory is garbage collected (node.js, java, etc ...), it allows handling a much bigger memory cache/store. In practice, very large heaps do not perform well with garbage collected languages.

• Redis can persist the data on disk if needed.

• Redis is a bit more than a simple cache: it provides various data structures, various item eviction policies, blocking queues, pub/sub, atomicity, Lua scripting, etc ...

• Redis can replicate its activity with a master/slave mechanism in order to implement high-availability.

Basically, if you need your application to scale on several nodes sharing the same data, then something like Redis (or any other remote key/value store) will be required.