Provisioned Throughput: Understanding Capacity Units

In Amazon DynamoDB, provisioned throughput is a key concept that determines the performance and scalability of your DynamoDB tables. It is essential to understand the concept of capacity units, as they play a crucial role in optimizing the read and write operations of your application. In this section, we'll explore provisioned throughput and capacity units in DynamoDB.

Provisioned Throughput:

Provisioned throughput refers to the amount of capacity you allocate for read and write operations on your DynamoDB table. It is expressed in two capacity units: Read Capacity Units (RCUs) and Write Capacity Units (WCUs). These units define the maximum number of reads and writes per second that your table can handle under normal operation.

Read Capacity Units (RCUs):

RCUs represent the maximum number of strongly consistent read operations per second that your table can support. A strongly consistent read ensures that you retrieve the most recent data from the table. By default, each RCU provides read access to one 4 KB item per second. You can adjust RCUs to meet the read requirements of your application.

Write Capacity Units (WCUs):

WCUs represent the maximum number of write operations per second that your table can handle. Each WCU allows you to write one 1 KB item per second. Similar to RCUs, you can adjust WCUs to meet the write requirements of your application.

Understanding Capacity Units:

Capacity units (RCUs and WCUs) are the currency used to pay for the provisioned throughput in DynamoDB. They determine the rate at which you can read and write data from and to your tables. By provisioning an appropriate amount of capacity units, you can ensure that your application can handle the expected workload efficiently.

How to calculate Capacity Units?

To determine the required number of capacity units for your application, you need to consider the size of your items, the expected read and write patterns, and the performance requirements. Here are some key points to keep in mind:

  1. Item Size: Each item's size affects the number of capacity units consumed. Larger items require more capacity units to read and write.
  2. Read Patterns: The number of read operations and their consistency requirements impact the required RCUs. If your application performs more read operations or requires strongly consistent reads, you need higher RCUs.
  3. Write Patterns: The number of write operations affects the required WCUs. If your application performs more frequent or larger write operations, you need higher WCUs.
  4. Burst Capacity: DynamoDB offers burst capacity that allows you to handle occasional spikes in traffic. Burst capacity credits are accumulated over time and can be used to accommodate short-term traffic bursts without requiring immediate scaling.

Scaling Provisioned Throughput:

You can scale provisioned throughput for your DynamoDB tables based on the changing needs of your application. You can increase or decrease the number of RCUs and WCUs through the AWS Management Console, AWS CLI, or API. DynamoDB can handle both immediate scaling needs and automatic scaling based on workload patterns.


Provisioned throughput and capacity units (RCUs and WCUs) are fundamental concepts in DynamoDB that determine the performance and scalability of your tables. By provisioning an appropriate amount of throughput capacity, you can ensure optimal read and write performance for your applications. Understanding the read and write patterns, item sizes, and adjusting capacity units accordingly will help you design efficient and responsive DynamoDB tables.

In the next article, we will explore auto scaling in DynamoDB, which allows for automated adjustment of capacity based on workload fluctuations. Stay tuned for more insights and best practices on working with Amazon DynamoDB!

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