I think you're understating the cost of updating the structure of an in-use data...

jrochkind1 · on March 10, 2015

I'm not even sure if you're referring to an rdbms or Mongo, which is kind of the other side there. I _think_ you're referring to an rdbms. But I also think people seriously understate the cost of changing the way your data is stored in a large in-use MongoDb too.

jacques_chester · on March 11, 2015

Mostly because an RDBMS will ask you to explain, explicitly, in complete detail, how you propose to consolidate the entire schema and existing data with the new changes without introducing paradoxes or inconsistencies.

Mongo won't. It will take you at your word. Even if that word is wrong.