Haskell & Elm. Deployed to AWS with NixOps. Persisted with PosgreSQL and Redis. Code hosted in either Bitbucket or GitHbub. Tasks managed with Trello and email. Occasional sync meetings over appear.in or Zoom (I travel).
Haskell and Elm both work great, but I can imagine in future using something like Haste or PureScript Bridge; it'd be nice to work with both the backend and UI as a single project. Not a pain currently, but this is a nice to have.
Biggest pain is documentation. Haskell stuff is documented, but more hand-holdy examples would be ideal. OTOH, some language communities have a culture of writing documentation that is too hand-holdy, flooded with emojis, and is generally frustratingly infantilising. I'd like Haskell to strike a balance between the two. I'm optimistic we'll get there eventually.