Consumer groups
A consumer group tracks one committed offset per partition. Everything behind that offset is safe to redeliver on restart.
Groups
| Group | Topic | Members | Lag | State |
|---|---|---|---|---|
| orders-search-idx | orders.updated | 4 | 0 | caught up |
| billing-ledger | billing.charged | 2 | 12 | caught up |
| audit-archiver | audit.trail | 6 | 310 | caught up |
| notify-dispatch | notify.outbound | 3 | 48,220 | falling behind |
| fraud-scoring | fraud.signals | 2 | 4 | caught up |
notify-dispatch lost a member at 03:40 UTC; the remaining two
can't clear the backlog alone. Restarting the third consumer is enough — no data is lost,
it resumes from its last committed offset.
Rebalancing
Partitions move between members when one joins or leaves the group. Reads pause on the moved partitions until the new owner confirms its starting offset — usually under a second, longer if the consumer is slow to commit.
Committing offsets
- Commit after the event is safely handled, not after it's read off the wire.
- Auto-commit on a timer is fine for idempotent consumers, risky otherwise.
- A group with no commits for 7 days is dropped and its offsets are not kept.