**Section 1 — The Context (The 'Why')**
Kafka-based real-time pipeline must achieve exactly-once. Windowing, enrichment, idempotent sink. At-least-once with non-idempotent sink causes duplicates.
**Section 2 — The Diagram**
```
[Kafka] --> [Consumer]
Partitions | Keys
|
v
[Spark Stream]
Windowing | Enrich
|
v
[Delta] Idempotent Merge
```
**Section 3 — Component Logic**
**Kafka** partitioned streams. **Spark Stream** windowing, enrichment....
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