A common language across front and backend systems is a huge benefit. I find it extremely productive to have a backend in Typescript on NodeJS, and a frontend in ReactJS, talking over a GraphQL layer where I'm autogenerating Typescript types from the GraphQL typedefs. Means I can share many libraries and tooling across the front and back ends, but most importantly it means devs feel much more comfortable digging into code on the other side. If a front end dev has an issue with a backend API call, he can just pull down the code and instantly inspect it and submit a PR of necessary without feeling "out of his element".