Of course, we could shard our underlying database instead of, or in addition to caching. If the database has a built-in in-memory cache, sharding the data would allow us to keep more of our data in working memory without an additional caching layer! Database sharding has some of the same challenges as cache sharding. Adding and removing shards can be painful, as can migrating the schema without site downtime. That said, some NoSQL databases have great sharding systems built right in, like Cassandra.