Throughput

Throughput measures how many messages a producer can publish, or a consumer can process, per second. It's the capacity metric that, combined with consumer lag, diagnoses whether a pipeline is healthy: consumption throughput lower than production throughput, sustained over time, is exactly what makes consumer lag grow indefinitely. Increasing consumption throughput usually means increasing parallelism (more partitions and consumers, Chapter 6) or reducing the processing cost per message — rarely does it mean tuning throughput without understanding which side is the bottleneck.