How does DynamoDB partition tables?

Question

The DynamoDB documentation describes how table partitioning works in principle, but its very light on specifics (i.e. numbers). Exactly how, and when, does DynamoDB table pa

Answer 1

I found this presentation produced by Rick Houlihan (Principal Solutions Architect DynamoDB) from AWS Loft San Franciso on 20th January 2016.

The presention is also on Youtube.

This slide provides the important detail on how/when table partitioning occurs:

And below I have generalised the equation you can plug your own values into.

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Partitions by capacity = (RCUs/3000) + (WCUs/1000)

Partitions by size = TableSizeInGB/10

Total Partitions = Take the largest of your Partitions by capacity and Partitions by size. Round this up to an integer.

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In summary a partition can contain a maximum of 3000 RCUs, 1000 WCUs and 10GB of data. Once partitions are created, RCUs, WCUs and data are spread evenly across them.

Note that, to the best of my knowledge, once you have created partitions, lowering RCUs, WCUs and removing data will not result in the removal of partitions. I don't currently have a reference for this.