The problem with Next.js App Router caching isn't memorizing flags. It's understanding what freshness each piece of data actually needs and treating that as an explicit contract — not as an isolated trick you reach for when something breaks.
React 19's use() hook promises to replace useEffect for data fetching. That promise is partially true. There are two patterns with Suspense and error boundaries where the behavior isn't what you expect and the cycle gets messier. I'll tell you exactly when to migrate and when not to.
The problem with App Router cache isn't memorizing flags. It's deciding what freshness each piece of data actually needs before you write a single line of configuration.
useEffect isn't broken — the mental model we teach with it is. I audited every useEffect in a React 19 codebase and found 4 concrete categories where it was an antipattern. Here are the patterns that replaced them: derived state, event handlers, use(), and Server Actions.
navigator.clipboard.writeText looks trivial until your app silently breaks in production with zero visible error. I found 4 cases the docs never mention: insecure context, lost focus, revoked permissions on iOS, and React timing. Here are the real patterns with copyable code.
I scored 98/100 on Lighthouse and axe on juanchi.dev. Then I asked someone who actually uses a screen reader to try it. What happened next embarrassed me. A perfect score and a real experience are two completely different things.
There's a deeply embedded belief in the dev community about AI in production that's just wrong: that you need an API, a server, and a credit card to add intelligence to your app. I ran it in the browser. No cloud. No billing. And now I can't stop thinking about what this means.
Brutal diagnosis, concrete changes, and real metrics. Here's how I took a Next.js app from embarrassingly slow to 300ms FCP — no magic, no excuses, just actual work.
An honest postmortem of building my portfolio with the freshest stack of 2025. Spoiler: almost everything broke. I rebuilt it anyway. Here's why it was worth every hit.
32 years in the dev trenches. Here I write what I learned, what I broke, and what nobody tells you in the tutorials.
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