I think I know the answer, but I'd like to confirm.
I've a 2-servers load balancer that's hosting a Wordpress website. When the content managers create new content, specially IMAGES: intermittently the image fail to load. After few refresh , it's loads fine.
So I decided to open both servers, and yes: There is no sync between servers. The WP website is not using S3 to store the media and a image may be in a server and sometimes not in the another.
How to solve this situation ?