Focusing on making things actually fast is always better than putting a cache or some hack on it.

Linear IS essentially a crud app so saying crud app does it in 300ms doesn't mean anything in this context imo.

If you have a database stack that is actually fast. And you can use something that is actually fast on the frontend like solidjs. Then you might have something that is actually fast.

But putting more complexity and caches etc. on top of it will leave you chasing issues that cause performance cliffs forever.

Modern hardware is insanely fast, this kind of complexity shouldn't ever be needed even if you consider each individual person is related to thousands of issues. I think most people have a home internet connection that is 100Mbps/s at least and they are on CPU with more than 4 cores and more ram than 8GB. And the frontend is running in a browser like chromium or firefox which is also insanely optimized.

Writing backend in JS, using postgres for database, then also using the clunkiest frameworks for the frontend and then writing something is highperformance is a really high level of delusion