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Valentyn Yefimov Blog

Practical engineering notes on React, Next.js, and scalable product development

In-depth posts about architecture, developer experience, performance, and lessons from building production software.

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PerformanceObserver concept image showing real user performance monitoring in modern web apps.

May 27, 2026 · 8min read

Stop Guessing, Start Measuring: Mastering PerformanceObserver for Modern Web Performance

If your performance strategy stops at Lighthouse and console timers, you are missing real-user bottlenecks. PerformanceObserver gives you production-grade visibility.

  • Web Performance
  • JavaScript
  • Core Web Vitals
  • RUM
  • Frontend
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Comparison chart showing when to use SSG, ISR, and SSR for public pages, ecommerce catalogs, user profiles, and live dashboards.

May 20, 2026 · 7min read

SSR vs SSG vs ISR and React Server Components: a practical Next.js guide

Rendering strategy is a product decision as much as a technical one. Here is how to choose SSR, SSG, ISR, and Server Components without overcomplicating the app.

  • Next.js
  • React
  • Frontend Architecture
  • Web Performance
  • Server Components
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Nine-layer frontend architecture diagram covering routing, views, state, UI library, API services, caching, supporting modules, observability, and build/deploy.

May 7, 2026 · 6min read

Most frontend architecture diagrams miss these 3 critical layers. Here's what I actually ship at enterprise scale.

Most architecture charts stop at components, state, and API calls. Real scalability needs nine layers and three often-missing ones.

  • Frontend Architecture
  • Enterprise Engineering
  • React
  • Observability
  • Web Performance
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Warning cover image about equipment scam and fake check scam in remote hiring.

April 30, 2026 · 6min read

Beware: the equipment scam and fake check scam in remote hiring

Scammers "hire" candidates quickly, then push them to pay for equipment or send money after a fake check deposit.

  • Scam Alert
  • Remote Work
  • Career Safety
  • Cybersecurity
  • Job Search
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AI economics concept highlighting that model compute can become more expensive than human labor.

April 29, 2026 · 3min read

AI is turning out to be more expensive than human labor

AI promised cheaper operations, but rising compute bills are forcing companies to ask whether humans are still more cost-effective for many tasks.

  • AI
  • Economics
  • ROI
  • Tech Strategy
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Cover image with TypeScript and JavaScript tips including satisfies, Object.groupBy, and closure patterns.

April 24, 2026 · 9min read

6 TypeScript and JavaScript tricks most developers still overlook

Five underrated JS/TS operators plus one advanced closure pattern that immediately improves correctness and readability.

  • TypeScript
  • JavaScript
  • Frontend
  • Code Quality
  • Performance
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The shadow market of GitHub stars article cover image.

April 20, 2026 · 7min read

The shadow market of GitHub stars

Fake-star markets now target startup hype cycles, especially in AI, distorting one of the most visible credibility metrics in open source.

  • GitHub
  • Open Source
  • AI
  • Startups
  • Venture Capital
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Article cover image for 10 underrated HTML features that improve app UX.

April 15, 2026 · 8min read

10 underrated HTML features that actually improve tour apps

From fetchpriority and popover to translate and enterkeyhint, these native HTML features remove hacks and improve UX.

  • HTML
  • Web Performance
  • Accessibility
  • Frontend
  • UX
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Cover image for article about native browser APIs replacing common JavaScript libraries.

March 27, 2026 · 10min read

3 more native Web APIs that replaced your favorite libraries

These three APIs handle modals, dates, and location with 0 KB and native browser reliability.

  • JavaScript
  • Web APIs
  • Performance
  • Frontend
  • React
  • TypeScript
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Article cover about a long-term freelancer account ban on Upwork and platform risk.

March 25, 2026 · 8min read

After 14 Years and $250,000 in fees, Upwork permanently banned me with zero explanation

After 14 years since Elance and around $250,000 in platform fees, the account was permanently deactivated without a clear explanation or meaningful appeal path.

  • Freelancing
  • Upwork
  • Gig Economy
  • Career
  • Remote Work
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GitHub-themed cover image representing malicious repositories used in hiring scams.

March 6, 2026 · 9min read

Scam targeting IT pros: malicious repos in the hiring process

Attackers are using fake hiring flows and malicious repos to compromise developer machines and steal tokens, keys, and environment secrets.

  • Cybersecurity
  • Developers
  • GitHub
  • Hiring
  • Security Awareness
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Dark interface style button with a rotating multicolor border and the text Button.

February 25, 2026 · 8min read

How to build a rotating conic-gradient button in vanilla CSS

Build a clean rotating gradient border button with @property, conic-gradient, and reduced-motion support.

  • CSS
  • Animation
  • Vanilla CSS
  • UI Engineering
  • Accessibility
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TanStack Hotkeys alpha banner with the title and subtitle about type-safe keyboard shortcuts.

February 25, 2026 · 7min read

TanStack Hotkeys: a better way to build keyboard-first UX in React apps

TanStack Hotkeys solves cross-platform shortcut bugs, sequence handling, and type-safety pain points for modern React applications.

  • React
  • TypeScript
  • TanStack
  • Developer Productivity
  • Frontend Architecture
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