It's 2021 and we have extremely fast key-value lookups using LevelDB/RocksDB, but we're still using RAM-based caching tools [1] [2] [3]. It's time to consider RAM-based caching harmful, and start caching with SSDs for larger datasets and lower costs. For ex: SSDB [4]
[1] https://redis.io/
[2] https://memcached.org/
[3] https://news.ycombinator.com/item?id=29532552
[4] https://github.com/ideawu/ssdb#ssdb-vs-redis