Backend & systems·Queues, streams and delivery semantics
you record the position you have processed up to, so restarting the consumer does not start it from the beginning again.
Offset
Also calledcursor, commit offset, checkpoint
The pointer marking how far a consumer has read in a partition. When you commit it decides your delivery semantics: committing before processing gives at-most-once, committing after gives at-least-once. Committing offsets on a timer while processing asynchronously is the usual way people get at-most-once by accident.