Firebase is one of the tools to use when time to market is cruicial. I have worked with firebase, firestore and google cloud functions regularely and I am proficient not only in using the features but do also know the best practices.
Everybody uses node.js. Is it in you buid chain, for the backend or serverless. I build robust backends in node.js for serverless environments like AWS Lambda, Google Cloud Funtions or directly on your server.
There is a ton of JS frameworks and it keeps growing day by day. I have choosen react to be my primary framework to work with and know most of the common mistakes and a whole lot of design patterns to structure even the most complex application.
Go is my first choice when it comes to small-ish - ideally containerized - services that are super performant and require parrelization. I have build smaller and larger services, either standallone or as a service mesh.