I've been using a lot of GCP services (App Engine, Firebase Auth, Cloud Firestore, etc..) for a website I'm working on, but lately I've been seriously considering the switch back to bog standard Linux (cron, bash, POSIX, systemd) instead of building upon a proprietary platform.
A lot of things are unnecessarily complex with my current setup. e.g., for batch jobs, I have a webserver which is pinged by a managed service, whereas a small binary + cron job could be easier to manage. Using a NoSQL database may be cheap with such tiny usage, but I'm missing the power of SQL, namely, integration with everything under the sun.
If you already know Python well, do Django or Django REST.
If you don't have any prior language affinities, go Javascript/Typescript on the whole stack. Language switching is a real problem for me.
I'd stick with App Engine/Heroku for prod. I like Postgres alot, especially with JSONB. Since it functions as a MongoDB-like database if needed.
If App Engine fails you, you should be able to switch to another provider very easily, or a standard VM without a code rewrite only a CI/CD rewrite
With that being said,I run a monorepo. /api folder has Feathers JS with Postgres /admin folder has react admin website /website folder has public facing react website.
Everything can run local during dev. Everything is CI/CD piped 12 factor styled One git push and merge to master, deploys everything. I love it.
If a single provider fails me, I can switch pretty easily.
If you want barebones minimalist stack and are comfortable with C++, then you can try Wt[0]. Wt is not a framework, it is a toolkit and actually works like Qt but for web development. And the team developing that are super helpful even though they are a small team.
If you want dynamic programming with virtual machine, then try Elixir or straight way go to Erlang.
For front-end I will prefer jQuery+Bootstrap, KnockoutJs or Svelte and use Unpoly[1] if doing server-side rendering. (These I am recommending because I am not a front-end developer, others may have better suggestion)
For mobile development, I would recommend Flutter for front-end and Dart and/or Kotlin and/or C++ for mobile middleware.
For DB, it is either PostgeSQL or CouchDB for me.
If you want to learn new tech, anything that catches your interest.
* Bootique (better Spring Boot),
* Vert.x (reactive framework and libraries for unmatched performance),
* Akka (for distributed coordination, if necessary; though depending on the use case, it might be simpler to just use external services, like Zookeeper or Consul -- Bootique has integration with those)
Honorable mention goes to Netty, which is great for high performance networking, but going so far is rarely needed in most servers.
I've not made the move but it's the most promising stack I've looked into.