Amazon Games deployed a server side patch on all the servers to help out with lag issues and server stability. There was no downtime required to apply this patch and it should make things better for everyone. If you are still experience "Lag Detected" issues in New World after 6pm PST, then please head over to the forums and let Amazon Games know you are still affected by this.
Additionally if you are unable to see your achievements, then you will need to log out of the game (character selection works) and wait 5 minutes before logging back into your character. This only happens when a server side patch occurs and the player's client isn't synced with the right version in the background.Here is the forum post
about the topic if you wish to see it for yourself.