How to clear backlog and monitor it

@BYK, I looked up the Queues using below. Are the worker processing messages in each of these topics ?
kafka-topics --list --zookeeper zookeeper:2181
__consumer_offsets
cdc
errors-replacements
event-replacements
events
ingest-attachments
ingest-events
ingest-sessions
ingest-transactions
outcomes
snuba-commit-log

I am not sure how to see the the highest load. Any pointers you can provide will help.