PHP /laravel and react.
In the past years Laravel has helped us quickly build prototypes that we could conveniently grow into enterprise-scale apps.
Backend: PHP/Laravel Frontend: Same, using VueJS as needed/wanted. Database: Usually starting off with SQLite and switch to a more appropriate choice like Postgres, MariaDB or even MSSQL.
If it wasn't for PHP I think Laravel would have overtook Rails as the tools to build prototypes.