Especially with the new(ish) DynamoDB features mentioned in this article (ex: adaptive scaling), the backup and restore capabilities including Point in Time Recovery, and on-demand pricing model, makes it a really effective database when going with the single table design.

Wrapping your head around this takes some pretty serious time along with trial and error. Work and rework your data model multiple times. Turning to spreadsheets actually tremendously helps with being able to define and move data around to play that game of Tetris mentioned in the article.

In addition, you'll probably want to avoid any of the common ORM type clients that exist for DynamoDB, they tend to have made decisions that make using a single table design an uphill battle. Write your own little wrapper for the native AWS DynamoDB client in your language of choice and you'll be much happier long term.