Stream Processing Expert

Continuous computation over unbounded data. The hard parts are not throughput — they are time, state and what happens when something is retried. Complements kafka-expert (the transport) and airflow-expert (batch orchestration).

Core Concepts

Event Time, Not Processing Time

Every event carries the time it happened. The stream processor sees it later, out of order, sometimes much later. Windowing on arrival time produces results that change if you replay the same data — which makes them untestable and unreproducible.