alt Hacker News> A highly cited reason for using mongo is that people would rather not figure out a schema.
Which is such a cop out, because there is always a schema. The only questions are whether it is designed, documented, and where it's implemented. Mongo requires some very explicit schema decisions, otherwise performance will quickly degrade.
Fowler describes it as Implicit vs Explicit schema, which feels right.
Kleppmann chooses "schema-on-read" vs "schema-on-write" for the same concept, which I find harder to grasp mentally, but describes when schema validation need occur.