It is an apples to oranges comparison, but it underlines, from a beginner perspective, the major differences between a pure key-value store (Project Voldemort) and a document database (Terrastore):
Being a simpler KV store than Terrastore, to my understanding Project
Voldemort offers no ability to leverage the server to evaluate the
Values. In order to, for example, produce a list of documents whose
“publish date” is in the past, it is necessary to either fetch all
documents and evaluate the publish date each time this operation is
needed — or — manage a lookup list of document IDs that were “published”
when the lookup list was created.
In the end, the author also emphasizes how important the first impression is: clean documentation, simple installation, etc.. Or differently put, an end user judges a project by how fast he can start using it.
Original title and link: Project Voldermort and Terrastore: Key-Value vs Document Stores (NoSQL databases © myNoSQL)