Kafka Message Flow
Producers append to partitions; a consumer group pulls each partition with one consumer.
Produced
0
Consumed
0
In flight
0
Partitions
4
Producer Partition Consumer In flight
Partition → consumer ownership
C00, 2
C11, 3
Each message goes to one partition (round-robin), then to that partition’s single consumer. A partition has exactly one consumer; a consumer may own several. The amber dots are in flight — watch the +n counts climb as flow moves left → right.
How this simulator works
Producers append to partitions; a consumer group pulls each partition with at most one consumer. Watch messages flow producer → partition → consumer.
Partitions and parallelism
- A partition is the unit of parallelism — one partition is consumed by exactly one consumer in a group.
- Adding consumers past the partition count leaves consumers idle.
- Adding partitions lets you scale consumption (and rebalances the group).
Ordering
Ordering is guaranteed within a partition, not across partitions. Keyed production keeps a key’s events on one partition and therefore ordered.