Memcached vs. Redis: Which is Right for Your Needs?

If you need to speed up a web app on AWS, you’ve probably bumped into Memcached and Redis. Both cache data in RAM so your database doesn’t have to work as hard. But they take different approaches, and knowing which one fits your situation matters.

How the Big Names Use Them

Amazon leans on Redis for product listings and user sessions. Twitter uses Memcached for tweets and profiles. Facebook caches friend lists and profile data with Redis. Netflix uses Memcached for movie and show info. Google caches search results with Redis. The pattern here: simpler key-value needs often go to Memcached, while richer data structures end up in Redis.

What Memcached Does Well

Brad Fitzpatrick built Memcached at LiveJournal back in 2003 when the site needed to scale. It’s straightforward: store key-value pairs in memory, retrieve them fast. No persistence, no fancy data structures. Just get, set, delete, increment, decrement.

On AWS ElastiCache, Memcached clusters scale horizontally. Add more nodes as traffic grows. The protocol is simple, and client libraries exist for pretty much every language. If you just need to cache database query results or session data, Memcached gets the job done without much overhead.

The trade-off: it’s bare-bones. You can’t persist data, and you’re limited to strings and integers. For some use cases, that’s exactly what you want.

What Makes Redis Different

Redis showed up in 2009 and took a different path. The name stands for Remote Dictionary Server, and it actually uses a dictionary data structure internally. But the real difference is what Redis can store: strings, lists, sets, sorted sets, hashes, bitmaps, hyperloglogs, and more.

On AWS ElastiCache, Redis offers both single-node and cluster modes. You can enable replication for high availability. Since 2023, AWS also supports Valkey as an engine option, which is Redis-compatible but open-source.

Redis handles persistence if you need it. You can also use it as a message broker with pub/sub, or for real-time analytics with sorted sets. The scripting support through Lua adds custom logic without external dependencies.

How They Stack Up

The Bottom Line

There’s no universal winner here. Pick Memcached if you want something lightweight that handles basic caching without complexity. It’s easier to scale horizontally and works well when you just need to store and retrieve values fast.

Go with Redis if you need more flexibility. When your cache needs to handle complex data types, support persistence, or act as more than just a cache, Redis has you covered. AWS ElastiCache manages both, so your operational overhead stays reasonable either way.

Try both with your actual workload if you can. The real-world performance difference depends heavily on your data access patterns.