This is more of a question to understand the architecture. If I have a containerized e-commerce web application, how would K8s make sure that different replicas of the application have the same information in sync?

For example, what if I use K8s to deploy the application and scale it and use a load balancer so I can optimally route traffic. Now, if I have two (or more) replicas of the application running, and the load balancer is actively dividing the traffic between the applications, how would I ensure data is in sync between the different replicas?

Like if I am routed to one replica and place an order there, and tomorrow I'm routed to another replica, how would I ensure that the second replica also shows I've placed an order and has all the data in sync with the other one?