> Get me all the content of slide Y of deck XXXX But that's not a query I ever need. I load the user's document, which contains an array of slide (embedded doc

> Get me all the content of slide Y of deck XXXX But that's not a query I ever need. I load the user's document, which contains an array of slide (embedded documents). There is no relation between documents & slides, slides are part of the document. But take it one step further & imagine you have a variety of widgets that can be placed on slides, with no common schema between them. Your choice is model out 100s of tables, use EAV, or go noSQL. We did the latter. > would make me itching for indices and foreign constraints Mongo has indexes. Regarding foreign keys it does not have that, but usually you can just embed the document in all the places you need it (de-normalization). Which can be a problem, so if you don't want de-normalization you should definitely use a SQL DB, not mongo. > Postgres's partial indices + indexes on expressions would make some fairly intricate reports like "since we launched the image embedding feature, per week, what percent of created or modified slides contain images" Mongo has aggregation which has fortunately been able to perform all the reporting I've needed so far. I'm sure postgres is nice as well.