Message Consumer

You might say

The message was sent, but the queue keeps growing. Check whether a consumer is receiving, processing, and acknowledging the messages.

A message consumer is an application or instance that receives messages from a queue, handles them according to its rules, and acknowledges their processing statusAn upload API can publish a transcoding task while a consumer takes it from the queue and runs the work. An order system can use a consumer to receive an order-created message and create a shipping record. Without a consumer, messages build up; if processing fails, a message may be delivered again, so successful publishing is not business completion.
Consumer
Further reading