RCU: Read Capacity Units

Learn what RCUs are and how to calculate them.

AWS offers a bunch of ways to charge companies. They depend on the service type, consumption rate and service models such as IaaS, PaaS or SaaS. As DynamoDB is a serverless database, charges are based on reads, writes and storage. However, there are some features that generate additional charges. In this lesson, we are going to explore how reads work in DynamoDB.

What is an RCU?

A read capacity unit (RCU) is the measurement unit that DynamoDB makes use of to provide the resources that it will use to support our workloads. The measurement unit is defined by record size and time. The first part to know is the size, which is a fixed block of 4 KB. The second part is the time, which is set to 1 second. Combining them together, we can define an RCU as a read of a block of information up to 4 KB in 1 second.

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