Producers can overwhelm consumers. You need flow control:
Backpressure: Signal to producers to slow down. Queue depth indicates consumer health.
Strategies:
- Rate limiting at producer
- Bounded queues that reject when full
- Consumer-controlled pull (Kafka model)
- Circuit breakers that stop sending when downstream fails
Monitoring: Track queue depth, processing latency, consumer lag. Alert before queues overflow.
Without backpressure, you get unbounded queues, memory exhaustion, and cascading failures.