Kafka: auto-commit commits on poll, not on success

The next poll commits the previous batch whether or not it was processed successfully.

Code

// enable.auto.commit=true, auto.commit.interval.ms=5000
var records = consumer.poll(...);   // may commit the PREVIOUS batch here
for (var r : records) {
    process(r);                     // throws on record 3 of 100
}

Output

Records 3 to 100 were never processed,
but their offsets are committed on the next poll and never redelivered.

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Published 2026-08-11