Delivery guarantee

At most once

This guarantee ensures that a message is delivered at most once, but there is a possibility that it may not be delivered at all.

At least once

This guarantee ensures that a message is delivered at least once, but it may be delivered multiple times.

Exactly once

This guarantee ensures that a message is delivered exactly once, and not more or less.

Links

• Article by Tyler Treat: You Cannot Have Exactly-Once Delivery