You should put some effort on designing the key schema, especially the hash key. Don't do timestamp, or sequence. I had to do a 'encrypted' key schema on my sequence IDs so sequential records are spread into different partitions. Actually it worked out well as I can exposed these encrypted keys externally too.

Agreed that DDB documentation could be better on the best practices. I found this deep dive youtube video very helpful: https://www.youtube.com/watch?v=VuKu23oZp9Q