DP-420 Question #167: Real Exam Question with Answer & Explanation

Question

You are designing an Azure Cosmos DB for NoSQL solution to store data from IoT devices. Writes from the devices will be occur every second. Data will be retained indefinitely. The following is a sample of the data. You need to select a partition key that meets the following requirements for writes: - Minimizes the partition skew - Avoids capacity limits - Avoids hot partitions What should you do?

Options

• AUse timestamp as the partition key.
• BCreate a new synthetic key that contains deviceId and sensor1Value.
• CCreate a new synthetic key that contains deviceId and deviceManufacturer.
• DCreate a new synthetic key that contains deviceId and a random number.

Explanation

Use a partition key with a random suffix. Distribute the workload more evenly is to append a random number at the end of the partition key value. When you distribute items in this way, you can perform parallel write operations across partitions. Incorrect Answers: A: You will also not like to partition the data on “DateTime”, because this will create a hot partition. Imagine you have partitioned the data on time, then for a given minute, all the calls will hit one partition. If you need to retrieve the data for a customer, then it will be a fan-out query because data may be distributed on all the partitions. B: Senser1Value has only two values. C: All the devices could have the same manufacturer. https://docs.microsoft.com/en-us/azure/cosmos-db/sql/synthetic-partition-keys

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