Um offset é um ID único e sequencial para cada evento dentro de uma partição — marcando sua posição. Consumidores rastreiam e confirmam offsets para saber o que consumiram, permitindo retomar, reproduzir e processar de forma confiável.
O que são offsets
OFFSET → the position/ID of an event within a PARTITION:
→ each partition is an ordered log; events get incrementing offsets (0, 1, 2, ...)
→ an offset uniquely identifies an event's position in its partition
→ events are RETAINED → the log keeps events (offsets remain valid for the retention period)
Como consumidores usam offsets
→ a consumer reads events in order and tracks its CURRENT offset (where it has read to)
→ COMMITTING an offset → records "I've processed up to here" → on restart, resume from
the committed offset (don't reprocess everything)
→ consumers can SEEK to any offset → REPLAY old events, skip ahead, reprocess from a point
→ each consumer GROUP tracks its own offsets per partition (independent progress)
