# Two streaming aggregators sit at opposite ends of the idempotency-cost spectrum, and their architect

Canonical URL: <https://datadriven.io/problems/two-streaming-aggregators-sit-at-opposite-ends-of-the-idempo-2c0f3731>

Domain: Pipeline Design · Difficulty: medium

## Problem

Two streaming aggregators sit at opposite ends of the idempotency-cost spectrum, and their architectures have been swapped. A financial-close pipeline whose output feeds an SEC report writes to a Redis counter; a real-time page-view counter for a five-second engagement dashboard runs Flink 2PC into Iceberg. Apply the section's three-question decision framework and put each aggregator on the architecture its use case actually justifies.

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