100% true, but in fairness work stealing doesn't completely solve that either. You often end up locking the shard anyway because lockless data structures are li

100% true, but in fairness work stealing doesn't completely solve that either. You often end up locking the shard anyway because lockless data structures are limited and hard. And if you're doing something like a key/value store, you're probably sharding to decide which server to direct traffic to, and so you have the same problem at that layer. (There are things that can help, of course, e.g. <https://aws.amazon.com/blogs/architecture/shuffle-sharding-massive-and-magical-fault-isolation/ https://aws.amazon.com/blogs/architecture/shuffle-sharding-m...>.)