Why is it possible to go beyond DynamoDB burst capacity?

Question

I have created a DynamoDB table with 1 RCU (manual provisioned capacity).

I have inserted some items to read in that table.

I can launch a scan on my table (which consumes 82 RCUs according to the response).

I understand this is possible because of the burst capacity.

What I don't understand though, is why am I able to keep consuming huge numbers of RCUs for long periods of time.

As you can see on this screenshot, despite the RCU being 1, I have been consuming around 150 or 200 RCU per minute for more than 1 hour (we can barely see the 1 RCU red line at the bottom).

Why is that? (some of the requests are of course throttled but why so little ?)

Answer 1

How much data do you have in that table? When you try scan operation from console, it will read items from the table that will consume RCUs.

There are options to configure baseline read/write capacity units and enable autoscaling if you expect variable reads/write requests. If the load starts to increase, dynamo db service will gradually scale to fulfil those requests instead of throttling.

https://aws.amazon.com/blogs/database/amazon-dynamodb-auto-scaling-performance-and-cost-optimization-at-any-scale/