DynamoDB: Papers

[msfidelis]

Including two more papers about DynamoDB Key Value Store and Amazon EBS

[facundoolano]

Hi Matheus, thanks for the PR. As per the selection criteria I try to keep the list short, including the most representative papers on each topic. These seem interesting but I'm not sure they would add much to the ones already in the "Internet Scale Data Systems" section.

(I assume most amazon and google services end up with an associated paper, and it wouldn't be convenient to include them all in the list. But let me know if there are particular reasons why you think these ones should)