Best advice will be to put a reverse proxy nginx routing certain calls to frontend, and certain to backend. Best way to build will be Docker images and a docker-compose file for starters, where you will define the database, the backend, the frontend, and the reverse proxy nginx, which you can configure to use certificates and certbot from Let's Encrypt. You can worry about performance later, at which point you will probably need to migrate towards Kubernetes. Standard setup with docker-compose should serve you well for up to 1000 users. You can initially use the same domain with possibly /v1 routing keys towards backend, and the rest towards frontend, which should be a plain Nginx image with all of the frontend files compiled. You can compile them using multi-stage Docker builds, or just plain CI/CD such as GitLab.
