Apache Spark vs Apache Flink: which should you use?

Databricks argues Apache Spark is the better default for most teams, since Real-Time Mode brings Spark streaming to millisecond end-to-end latency and removes the main reason teams added Flink. In Databricks' published benchmark at 10,000 records per second, Spark Real-Time Mode matched Flink on stateless work (3 ms p99) and beat it on stateful aggregation (14 ms vs 45 ms) and stream-static joins (9 ms vs 95 ms). Flink remains a fit for very large keyed state, complex event processing and event-time timers, but adopting it usually means operating a second engine alongside Spark.