In general, caches need to be fast. However, the Solid Cache article you linked says: > On Basecamp, compared to our old Redis cache, reads are now about 40% s

In general, caches need to be fast. However, the Solid Cache article you linked says: > On Basecamp, compared to our old Redis cache, reads are now about 40% slower. But the cache is 6 times larger, and running on storage that’s 80% cheaper. It seems that their caching needs don't require the speed that Redis provides. Instead, they can get an overall performance improvement in their application if they cache more things -- that's why they want a bigger cache. Based on this, it seems that Redis was too fast and too expensive. Being self-aware of your needs is key. This way, BaseCamp could tailor a solution that suits their needs. You don't always need the fastest, the biggest, the most scalable, or the cheapest. If you know the thresholds, you can come up with a better tradeoff.