The hard 400kb per item limit does sort of force a pause to make sure it will still work well over the lifetime of the app. Not that huge "rows" are a good idea, but that's roughly 2 pages of text.

I think it's more like 200 pages of text -- 2kB/page is what I've always worked off.

Heh, yep. Missed some magnitude there. Argh. Though still something to consider, like pulling from SQS could use most of the item space for example.

Dynamodb is very scalable and effective at keeping operational cost down. It succeeds at it's goals by trading off on lots of things though. As a developer it can feel almost hostile. Adhoc queries are limited almost forcing you to have a complete second copy of the data. Access patterns must be designed up front and hope you don't need to change much when you hit scale. The tooling is meh. It's easier to make a scalable database when you push all those problems on your devs. Constraints are tricky. Transactions must be carefully designed. It's nice to know that almost definitely read and write throughput will scale and you can reduce the DBA/DevOps staff because AWS handles it.