Why DynamoDB did not reject when ConsumedCapacity exceeding the Provisioned Throughput?

Question

recently I was using DynamoDB to build my service. I use the provisioned mode for my DynamoDB table.

In order to test how DynamoDB will react, I set both Read Capacity Unit and Write Capacity Unit to only 1. In addition, I insert 20 items which account for about 27KB in my table. I use Scan method with ReturnConsumedCapacity parameter. I use Postman to test it, the result shows that it consumes 2.5 capacity units!

Why does DynamoDB not reject my request? I only assign 1 to both RU & WU! Doesn't it mean that it should only be able to read as much as 4KB of data in one second?

This is the screenshot of Postman result

Answer 1

Reference -
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.ReadWriteCapacityMode.html#HowItWorks.ProvisionedThroughput.Manual

One read request unit represents one strongly consistent read request, or two eventually consistent read requests, for an item up to 4 KB in size. Transactional read requests require 2 read request units to perform one read for items up to 4 KB. If you need to read an item that is larger than 4 KB, DynamoDB needs additional read request units. The total number of read request units required depends on the item size, and whether you want an eventually consistent or strongly consistent read. For example, if your item size is 8 KB, you require 2 read request units to sustain one strongly consistent read, 1 read request unit if you choose eventually consistent reads, or 4 read request units for a transactional read request.