What behavior is the application MOST likely exhibiting to users?
Users cannot add any items to the shopping cart.
Users intermittently notice that the cart is not updated correctly.
Users cannot remove any items from the shopping cart.
Users cannot use the application because it is falling back to an error page.
Explanations:
The high AuroraReplicaLagMaximum metric indicates a delay in replication from the primary DB to the replica, but it does not indicate that users cannot add items to the shopping cart. The issue is more likely to affect data freshness and consistency, not complete functionality.
High replica lag would lead to delayed data being reflected on the replica, which could cause users to intermittently see outdated cart information. This matches the behavior described in the question, where the cart may not update correctly.
While high replica lag might affect reading the most recent cart data, it would not completely prevent users from removing items from the cart, as the remove operation might still be processed by the primary database directly.
The application falling back to an error page would be indicative of a more severe issue such as database unavailability or connection issues, not high replica lag. High lag typically affects data consistency, not total failure of the application.
I strategize that the answer is:
Users intermittently notice that the cart is not updated correctly.