Request Units and Cosmos DB Account Modes

Introduction to request units

Request units (RUs) are essential to Cosmos DB’s billing strategy because we are billed based on the RUs consumed. Each RU abstracts a resource consumption, like CPU, memory, or input/output operations per second (IOPS), and each operation consumes a specific amount of RUs, influenced by document size, query complexity, indexing policies, and more.

During this course, we’ll see which other factors influence consumption and how to optimize it.

Account modes

How Azure uses RUs against us is determined by the mode selected on our Cosmos DB account. We specify the mode during the creation of the account, and the possible options are “Serverless” and “Provisioned throughput.” Below is an example of the Azure portal panel for creating a new account, where we have to choose the two capacity modes.