The Server Action That Ran Twice, but Only on localhost
Why a Next.js Server Action called from useEffect runs twice in development: React Strict Mode mounts every component twice. What that reveals, and where the call belongs.
4 min read
Why a Next.js Server Action called from useEffect runs twice in development: React Strict Mode mounts every component twice. What that reveals, and where the call belongs.
A bug report, a route map, and three rounds of making it faster — a story about what Big O really measures, why constants win at small n, and why the best algorithm is sometimes deleting the question.
Why your effect reads old state, fires twice, or loops forever — and the simple rules to fix it (interview-ready).
Three React APIs that all say 'memoize' — but they do different things. Clear explanations, examples, and a cheatsheet.
How useDeferredValue works under the hood, when to use it, and how it differs from useTransition.
How useTransition works under the hood, when to use it, and how it differs from useDeferredValue.
A deep but clear explanation of React Fiber — the engine that powers modern React rendering and concurrency.
Understand what React Context is, how it works internally, and best practices for using it effectively.
Understanding why calling setState after hydration doesn’t produce hydration mismatches in React/Next.js.
Everything you need to cancel async work in JS: fetch, streams, custom tasks, React patterns, Node notes, timeouts, races, and common pitfalls.
Deep dive into React's useState, how it works internally, and why client components are required in Next.js App Router.
Understand 'use client' in Next.js App Router: what it means, when to use it, and how it works under the hood.
Understand the key differences between the old Page Router and the new App Router in Next.js.
A polished, practical event bus pattern with minimal JS, a strongly-typed TS version, wildcards, once-handlers, and React usage tips.
Understand Higher-Order Components (HOCs) in React with examples, use cases, downsides, and a comparison to hooks.
A simple guide to understanding when to use useRef and useState in React, with examples, mental models, and a quick cheatsheet.
A practical guide to dynamic imports with real-world examples and a before/after bundle-size comparison using next-bundle-analyzer.
A concise, example‑driven overview of the most useful frontend patterns for modern React/Next.js apps.
Clear, practical explanations of MVVM, micro‑frontends, and domain‑driven design for modern React/Next.js teams, with examples, folder structures, and trade‑offs.