15.41Beware duplicate consumers during deployment

This is a very important integration-specific concern.

Suppose both old and new app versions temporarily consume:

same queue

during rollout.

Could both process the same message?

Depends on broker/deployment semantics.

Or suppose both run:

Scheduler every 5 minutes

during overlapping deployment.

Could the nightly sync run twice?

This is why:

idempotency
locking
scheduler semantics
consumer design

matter during deployments too.

Great interview point.