Nice of you to mention developer velocity: it is extremely important, and it's also severely impacted by things that depend on the framework having good performance, such as initialisation time, development-time performance (it's important to have a quick feedback loop), time required to run individual tests (important for TDD), time required to run the whole test suite (running it often saves developers time during refactoring), time required to compile assets, time for the CI/CD to run (important to allow quick and safe bug fixes and a fast process), etc.
Once your app stops being trivial, those things start adding up and people start talking about migrating to something else, breaking the app into microservices, or developing in-house tooling. All those things cost money. It might take a few months but it happens. And I've seen over and over.
Also, having horizontal scaling is definitely not easy for non-trivial apps. It costs money to the company, might require extra employees, and might put a hold on new features. And horizontal scaling doesn't help you with performance time or developer velocity.
Also please keep in mind that performance and developer velocity are not at odds. Most of today's "fast" frameworks are quite good when it comes to developer velocity: ASP.NET Core for instance is #6 on the Techempower framework and is incredibly productive.
Is this one of those RomComs where we are screaming at each other in agreement?
Horizontal scaling of course isn't binary and using a remote state store, preferably with CRDTs or strong consistency will allow _most_ applications to remove a spof and single node perf from dominating.
Everything you said is spot on, except for your dismissal that horizontal scaling should be first class. It might have been hard before, but we no longer have an excuse. Store your state in a modern distributed store.
> Developer velocity matters way more than the framework as long as the framework allows for horizontal scaling
I disagree with that. Both because developer velocity is not unrelated to framework performance, and because horizontal scaling is not a silver bullet that will magically solve the performance issues related to framework code.
Once your app stops being trivial, those things start adding up and people start talking about migrating to something else, breaking the app into microservices, or developing in-house tooling. All those things cost money. It might take a few months but it happens. And I've seen over and over.
Also, having horizontal scaling is definitely not easy for non-trivial apps. It costs money to the company, might require extra employees, and might put a hold on new features. And horizontal scaling doesn't help you with performance time or developer velocity.
Also please keep in mind that performance and developer velocity are not at odds. Most of today's "fast" frameworks are quite good when it comes to developer velocity: ASP.NET Core for instance is #6 on the Techempower framework and is incredibly productive.