Exactly. The race condition problem from the example below still exists even without any caching, and perhaps still exists even without any replica.

> Imagine that after shuffling Alice’s primary message store from region 2 to region 1, two people, Bob and Mary, both sent messages to Alice. When Bob sent a message to Alice, the system queried the TAO replica in a region close to where Bob lives and sent the message to region 1. When Mary sent a message to Alice, it queried the TAO replica in a region close to where Mary lives, hit the inconsistent TAO replica, and sent the message to region 2. Mary and Bob sent their messages to different regions, and neither region/store had a complete copy of Alice’s messages.

A solution to this problem is to update Alice's primary message store to be "region 2;region 1" for a period of time, and get Alice to retrieve messages from both message stores during that period.

However, since you have a caching layer that doesn't have an explicit TTL, such that any cache inconsistency can last indefinitely, you now have a much bigger distributed data problem.