What is your definition of lean? Each of the components in the MEAN stack have been tried and tested through many a applications deployed to prodcution already. Also, to answer your question- Yes, the components of the MEAN stack can be replaced.
Mongo with Couch
Express with Hapi/Koa
Angular with Backbone/Ember
Would you turn that thing down? I'm controlling a mind here! Look ... look at the tiny ad ...
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