Stream Processing

Problem

Fraud detection needs to react to a suspicious payment now. Waiting for tonight's batch job is too late.

Solution — Stream Processing

Process events continuously as they arrive. A stream here is an ongoing sequence of records: payments, sensor readings, log entries, or database changes. Each record can arrive through an HTTPS request or a messaging system; the processor works on the arriving data, for example tracking each card's spending over the last five minutes. The key is continuous computation over incoming records; the transport can vary.

Payment
   ↓
Event stream
   ↓
Fraud processor
   ↓
decision

Core idea: stream processing computes over continuously arriving data rather than waiting for batches.