Monitor oldest unfulfilled batch request

Question

I have a system with multiple components say A, B and C. All these are running as different deployments. "A" consumes msg from pubsub and passes it to "B" for further processing and the result is passed to "C".

Question: I want to track time as "A" consumes msg and raise an alert if "C" didn't receive the result for any of the consumed msgs < x hrs. The functionality is similar to "Oldest unacked message age" monitoring for google pubsub but for K8s deployment