Originally published November 7, 2017 at ObjectRocket.com/blog.
This post explains some of the most common Redis™ use cases and different characteristics that influence these choices.
1. Session cache
One of the most apparent use cases for Redis is using it as a session cache. The advantage of using Redis over other session stores, such as Memcached, is that Redis offers persistence. While maintaining a cache isn’t typically mission-critical with regards to consistency, most users might be upset if all their cart sessions go away.
Luckily, with the steam Redis has picked up over the years, you can easily find documentation on how to use Redis appropriately for session caching. Even Magento®, the well-known e-commerce platform, has a plug-in for Redis.
2. Full-page cache
Outside of your basic session tokens, Redis provides a straightforward Full-page cache (FPC) platform in which to operate. Consistency factors here, too. Even across restarts of Redis instances, with disk persistence, your users don’t see a decrease in speed for their page loads—a drastic change from something similar to PHP native FPC.
Magento offers a plug-in to use Redis as a full page cache backend.
For WordPress® users, Pantheon™ has an excellent plug-in, wp-redis, to help you achieve the fastest page loads you’ve ever seen!
3. Queues
Taking advantage of the Redis in-memory storage engine to-do list and set operations makes Redis a fantastic platform to use for a message queue. Interacting with Redis as a queue should feel native to anyone used to using push/pop operations with lists in programming languages such as Python®.
If you do a Google search on Redis queues, you can see that there are tons of open-source projects aimed at making Redis the backend utility for all your queuing needs. Celery, for example, has a backend using Redis as a broker that you can check out.
4. Leaderboards and counting
Redis does a great job with increments and decrements because it’s in-memory. Sets and sorted sets also make our lives easier when we do these kinds of operations. Redis just so happens to offer both of these data structures. So to pull the top 10 users from a sorted set—we’ll call it “user_scores”—you can run the following code:
ZRANGE user_scores 0 10
Of course, this assumes you’re ranking users on an incremental score. If you wanted to return both the users and their score, you could run the following code:
ZRANGE user_scores 0 10 WITHSCORES
Agora Games has an example, using Ruby, of a leaderboard using Redis as it’s datastore.
5. Publish-Subscribe
Redis has a Publish-Subscribe (Pub/Sub) feature. The use cases for Pub/Sub are boundless. I’ve seen people use it for social network connections, for triggering scripts based on Pub/Sub events, and even for a chat system built using Redis Pub/Sub!
Of all the features Redis provides, I feel like this one always gets the least amount of love, even though it has so much to offer users.
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