Is it really an application if it’s not stateful? Maybe you’re managing the state client-side which makes it easier but I wouldn’t call a plain website an application, or am I missing something?
At the smallest level, even every byte of an in-flight HTTP request is still state. State, and for that matter "uptime" really depend on what the application/service ultimately does and what the agreement/SLA with the end-customer is.
The correct high-availability solution should take business requirements into account and there is no silver bullet. Running everything on a $5 VPS is no silver bullet, but neither is your typical "cloud-native" "best practice" stack that everyone keeps cargo-culting which often leads to unnecessary cost while leaving many hard questions (such as replicating CAP-bound stateful databases) unanswered.
The correct high-availability solution should take business requirements into account and there is no silver bullet. Running everything on a $5 VPS is no silver bullet, but neither is your typical "cloud-native" "best practice" stack that everyone keeps cargo-culting which often leads to unnecessary cost while leaving many hard questions (such as replicating CAP-bound stateful databases) unanswered.