Consumer lag increases steadily due to slow processing

Consumer lag increases steadily, indicating consumer cannot keep up with producer throughput. Common causes: inefficient processing logic, insufficient resources, slow downstream dependencies. Alert when max lag >100,000 messages for 5+ minutes (warning) or >500,000 messages / increasing >50,000 msg/min (critical).

Scale consumers horizontally by adding more consumer instances, or optimize processing logic. Add retries, timeouts, and circuit breakers for downstream dependencies. Profile consumer code for bottlenecks.