For speed of development, you want the most normal/boring stack there is, in combination with what you're familiar with. Note that if there is more than 1 engi

For speed of development, you want the most normal/boring stack there is, in combination with what you're familiar with. Note that if there is more than 1 engineer, it is absolutely worth it to work with common technologies. Elm/Elixir are not common technologies (though people love talking about them). Node + Express for the backend is super simple. Mongo or MySQL/PostgreSQL you will have no problems with (though I am biased towards relational databases) React for the front-end is also simple, very well known and easy to hire for. If your application is more basic or more CRUD-oriented (as most apps are), Ruby on Rails has always been a solid choice and will continue to be a solid choice for years to come. There is also a very large pool of people who are very well-versed with it.