Complex Event Processing

Detecting meaningful patterns across millions of events in real-time — like "3 failed logins from different IPs within 5 minutes" triggering a fraud alert.

Key Takeaways

1. CEP detects patterns across multiple events in real-time — combining, correlating, and aggregating streams to identify meaningful situations
2. Temporal patterns are key — "3 failed logins within 5 minutes from different IPs" requires time-window awareness that simple event handling can't provide
3. CEP engines (Esper, Flink CEP, Drools) provide pattern-matching DSLs — expressing complex rules declaratively rather than in procedural code
4. Used for fraud detection, IoT monitoring, and algorithmic trading — any domain where real-time pattern detection drives automated decisions