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Describe core data concepts →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is the `iothub-connection-device-id` system property. This property is automatically injected by Azure IoT Hub into every device-to-cloud message, making it the correct field to reference in a Stream Analytics query when you need to filter IoT Hub messages by device ID. In your query, you would write a WHERE clause such as `WHERE iothub-connection-device-id = 'device-01'` to route only that device’s messages to a separate storage container for compliance. On the Microsoft Azure Data Fundamentals DP-900 exam, this tests your understanding of how IoT Hub enriches messages with system properties before they reach Stream Analytics, and a common trap is confusing this with the device’s telemetry payload or the Event Hubs partition key. Remember the memory tip: “connection-device-id” is the IoT Hub’s built-in stamp on every message, so always look for the “iothub-connection” prefix when filtering by device.

DP-900 Describe core data concepts Practice Question

This DP-900 practice question tests your understanding of describe core data concepts. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

Exhibit

{
  "consumerGroup": "$Default",
  "partitionId": "0",
  "sequenceNumber": 12345,
  "offset": "123456789",
  "enqueuedTimeUtc": "2025-03-25T10:30:00.000Z",
  "properties": {
    "systemProperties": {
      "iothub-connection-device-id": "device-01",
      "iothub-connection-auth-method": "{\"scope\":\"device\",\"type\":\"sas\",\"issuer\":\"iothub\"}",
      "iothub-enqueuedtime": "2025-03-25T10:30:00.000Z"
    }
  },
  "body": {"temperature": 25.5, "humidity": 60}
}

Refer to the exhibit. You are analyzing a message from an IoT device captured in Azure Event Hubs. The message contains system properties indicating the device ID and authentication method. You need to route messages from device-01 to a separate storage container for compliance. Which property should you use in a Stream Analytics query to filter messages?

Question 1hardmultiple choice
Review the full routing breakdown →

Exhibit

{
  "consumerGroup": "$Default",
  "partitionId": "0",
  "sequenceNumber": 12345,
  "offset": "123456789",
  "enqueuedTimeUtc": "2025-03-25T10:30:00.000Z",
  "properties": {
    "systemProperties": {
      "iothub-connection-device-id": "device-01",
      "iothub-connection-auth-method": "{\"scope\":\"device\",\"type\":\"sas\",\"issuer\":\"iothub\"}",
      "iothub-enqueuedtime": "2025-03-25T10:30:00.000Z"
    }
  },
  "body": {"temperature": 25.5, "humidity": 60}
}

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

iothub-connection-device-id

Option C is correct because the `iothub-connection-device-id` system property is automatically added by Azure IoT Hub to every device-to-cloud message. In a Stream Analytics query, you can reference this property directly (e.g., `WHERE iothub-connection-device-id = 'device-01'`) to filter messages from a specific device for routing to a separate storage container for compliance.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • ✗

    partitionId

    Why it's wrong here

    Partition ID is a system property of Event Hubs, not related to the device identity.

  • ✗

    consumerGroup

    Why it's wrong here

    Consumer group is a logical entity; it does not identify the device.

  • ✓

    iothub-connection-device-id

    Why this is correct

    This system property contains the device ID and can be used in a WHERE clause to filter messages from device-01.

    Related concept

    Read the scenario before looking for a memorised answer.

  • ✗

    deviceId

    Why it's wrong here

    The property is named 'iothub-connection-device-id', not 'deviceId'.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Microsoft often tests the exact naming of Azure IoT Hub system properties, and the trap here is that candidates assume a simple `deviceId` property exists, but the actual property name includes the `iothub-connection-` prefix, which is specific to IoT Hub's message enrichment.

Detailed technical explanation

How to think about this question

Under the hood, Azure IoT Hub injects system properties like `iothub-connection-device-id`, `iothub-connection-auth-method`, and `iothub-connection-auth-generation-id` into the message envelope when a device sends telemetry. These properties are accessible in Stream Analytics via the `IoTHub` input alias without any custom parsing. A real-world scenario: if you need to archive all messages from a specific device to a cold storage blob for regulatory audits, you can use a Stream Analytics query with `WHERE iothub-connection-device-id = 'device-01'` and a `SELECT INTO` output to a blob storage container.

KKey Concepts to Remember

  • Read the scenario before looking for a memorised answer.
  • Find the constraint that changes the correct option.
  • Eliminate answers that are true in general but not in this case.

TExam Day Tips

  • Watch for words such as best, first, most likely and least administrative effort.
  • Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Real-world example

How this comes up in practice

A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this DP-900 question test?

Describe core data concepts — This question tests Describe core data concepts — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: iothub-connection-device-id — Option C is correct because the `iothub-connection-device-id` system property is automatically added by Azure IoT Hub to every device-to-cloud message. In a Stream Analytics query, you can reference this property directly (e.g., `WHERE iothub-connection-device-id = 'device-01'`) to filter messages from a specific device for routing to a separate storage container for compliance.

What should I do if I get this DP-900 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jun 30, 2026

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