I would use .NET 6 (aka cross-platform .NET Core) for the backend, and I would do as much server-side rendering, simple forms, and the PRG pattern as I can. Minimal javascript, JS frameworks (maybe React) for highly-interactive pages. Standard RDBMS (likely Sql Server), with some initial planning on how to achieve horizontal scale as the clientbase grows, but not get too lost in the weeds on planning for a future that may never come. Maybe sprinkle in some Redis, a cloud queue/service bus, and some blob storage as needed.
Comments
I would use .NET 6 (aka cross-platform .NET Core) for the backend, and I would do as much server-side rendering, simple forms, and the PRG pattern as I can. Minimal javascript, JS frameworks (maybe React) for highly-interactive pages. Standard RDBMS (likely Sql Server), with some initial planning on how to achieve horizontal scale as the clientbase grows, but not get too lost in the weeds on planning for a future that may never come. Maybe sprinkle in some Redis, a cloud queue/service bus, and some blob storage as needed.