You have asked a "religious" question and you are therefore going to get a lot of very "religious" answers. The most important starting point is that you have something demonstrably working on some (any) language/framework. Now let's talk about "stacks". The MEAN "platform", isn't really that. It's just a bunch of tools that people have glued together and given a fancy name. It's not "designed to go together" in any particular way. Angular: this is just a front-end framework among many. It doesn't really care if you're using Node or .NET or Erlang. It's particularly designed for doing single page apps. There are other equally capable competitors in this space: React.js (backed by Facebook), Durandal.js, Backbone, Aurelia, Ember, etc. Express / Node: these are the server-side language and framework. Express is a relatively lightweight MVC framework, but there are lots of alternatives (The Future of ExpressJS and Alternatives). And there are people who build on top of Express (krakenjs - Give your node.js express apps some extra arms). MongoDB: this is the hot DB of the day. But frankly, it's not particularly good (Why you should never, ever, ever use MongoDB). People talk about how nice it is to "just save JSON", but everyone actually uses Mongoose, so that's a pretty lame argument. (Before you think I'm just a hater, I'm currently #3 on StackOverflow 'mongodb' Top Users) MongoDB is a useful tool to learn, but 95%+ of the organizations out there are using an SQL database. So if you have to pick between MongoDB and MySQL, you need to understand SQL. MongoDB is just "nice to have". Once you break this all up, you'll realize that you're actually asking a question about a lot of different technologies. And once you realize that there are lots of substitutions available, you can start to see what good employers really care about. Front-end framework: it's good to know one of these. Whether it's Angular or something else. At my day job we currently use Backbone, but we don't throw out your application just because you only know Angular. Server-side MVC framework: you should know one of these. The world communicates in APIs and this is how you build REST APIs. Node.js is the same language (javascript) as your client. That is its only real advantage. That's a pretty minor advantage. If your REST API is written in Nitrogen/Erlang, the Angular side doesn't really care and works the same. So frankly, the language you pick here is really up to you. Database Layer: you should know SQL. Knowing other competitive technologies (Cassandra/Riak/MongoDB) is nice to have, but nowhere near as important. The most important thing is that you have built a useful application using some set of modern tools. If people are turning away your resume because you know Angular.js instead of React.js or Node.js instead of C#, those people are doing you a favour. You don't want to work for people who cannot differentiate between "delivering a product" (really important) and language used (secondary).
