Ten thousand refrigeration units in supermarkets report their temperature every thirty seconds. Each unit must also be able to close a valve within a second of a reading going out of range — including while the shop's internet connection is down — and its telemetry should still reach AWS once the link returns. Which design fits?
AWS Certified Cloud Practitioner (CLF-C02), objective 3. Cloud technology and services hard
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The options
Correct AWS IoT Greengrass running on a gateway in each shop, connected to AWS IoT Core
Correct. Greengrass runs the messaging, the logic and even machine learning locally on hardware at the edge, so the valve decision is made in the shop and does not depend on the link, and it synchronises with AWS IoT Core when connectivity returns.
Not correct AWS IoT Core alone, with rules that act on each reading
Wrong for the offline requirement. IoT Core is the managed connectivity, device registry and message broker, and its rules engine runs in the Region — so while the shop's link is down, no decision is made at all.
Not correct A Lambda function invoked for every reading
Wrong on the same point, plus economics. Lambda runs in the Region, so it has the same dependency on the link, and a control decision that belongs a metre from the valve would be made a continent away.
Not correct Amazon Kinesis Data Streams collecting the readings
Wrong. It ingests and buffers streaming data inside AWS. It neither manages device connections and identities nor runs any logic in the supermarket.
Why
The two Internet of Things services split along one line: AWS IoT Core is the front door in the cloud — device identity, MQTT messaging, a device shadow and a rules engine that routes messages onward — while AWS IoT Greengrass takes that programming model out to hardware at the edge so devices can act locally and operate through a broken link. It is the hybrid deployment model in miniature: the part that must keep working without the cloud stays where the physical thing is.
Where this comes from
- Cited
- AWS exam guide task statement 3.8
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