Request Unit (RU)
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Category: Core Concepts
Summary: Normalized currency measuring the cost of database operations, independent of hardware.
Overview
A Request Unit (RU) is the normalized currency Azure Cosmos DB uses to measure the cost of database operations (reads, writes, queries) regardless of the underlying CPU, memory, or IOPS consumed. Every operation has an RU cost, and throughput is provisioned (or consumed, for serverless) in RUs per second (RU/s). Understanding RU cost is central to designing efficient partition keys, indexing policies, and queries for the DP-420 exam.
More Info & Links
DP-420 Style Practice Questions
Q1. What does a Request Unit (RU) measure in Azure Cosmos DB?
- A. The normalized cost of database operations, independent of underlying hardware
- B. The number of documents stored in a container
- C. The number of regions a database is replicated to
- D. The size of an index in megabytes
Q2. Which factor would generally increase the RU cost of a query?
- A. Scanning a large number of items due to a cross-partition query
- B. Reducing the number of properties in a document
- C. Using a smaller partition key value
- D. Disabling the analytical store
Answer Key
Answers are listed at the very end so you can attempt the questions first.
- Q1 (Request Unit (RU)): A. The normalized cost of database operations, independent of underlying hardware — RUs are a normalized measure of the cost of database operations such as reads, writes, and queries.
- Q2 (Request Unit (RU)): A. Scanning a large number of items due to a cross-partition query — Cross-partition queries that scan many items typically consume more RUs than efficient, targeted queries.
DP-420: Designing and Implementing Cloud-Native Applications Using Microsoft Azure Cosmos DB — term detail page
