10.54Transaction boundary with queue

A hard problem:

save database record
↓
publish message

What if DB succeeds but message publish fails?

Or message succeeds but DB transaction rolls back?

This is why patterns such as:

transactional outbox

exist.

You don't need to implement one during this interview unless they go deep, but recognize the issue:

Writing state and publishing an event are two separate side effects unless designed transactionally.