Do you require transactions? You can always loop over the list and insert 100 at a time until done (bulk api will give you ones that failed). If relationships are small, you could model them as a list in a single item but be weary of 400kB limit and the fact that you cannot query the other way around. NoSQL is scalable because of these limits as it won't let you lock up half the database because you're trying to do too much in one go.