[vtemian]

Serverless all the way. There are a lot of good options out there, with AWS being quite flexible.

The onboarding for other developers is also painless. I've recently experiment with AWS Amplify and even if is not quite there yet, is pretty close.

Lambda, cloudfunctions, https://supabase.com/, https://hasura.io/, AWS Amplify, https://aws.amazon.com/serverless/.

For frontend, I would go with either React or Vue, both with a huge community and already a lot of builtin solutions. I would 100% start with a design system, maybe material UI.

Nothing fancy, low maintenance and painless onboarding/development experience.