Sergei Usachev

About

I'm Sergei,
a frontend engineer.

Based in Serbia. I’ve been building websites and web apps with React and TypeScript for 5.5+ years.

About

Hi, I'm Sergei

Open to new opportunities

I’m a frontend developer with 5.5+ years of commercial experience in React, Next.js and TypeScript. I’ve started projects from an empty repo and taken over old codebases that needed cleaning up, and I like both.

What I pay attention to: pages that load fast, animations that don’t stutter, forms that work from the keyboard and layouts that don’t break on a small phone.

Based in
Serbia
Experience
5.5+ years
Languages
EN · RU
Education
Engineering

Experience

Full resume
  1. 2022 — 2026

    Space307 · Frontend Developer

    Built an internal HR system from scratch, led the page-by-page migration from Symfony to React and turned an internal CRM into a template adopted by 7 teams.

  2. 2021 — 2022

    Greenatom · Frontend Developer

    Worked on a self-service HR portal used daily by 50,000+ employees: org chart with search, real-time modules on RxJS, simpler request forms.

Off the clock

  • 01

    Music

  • 02

    Photography

    • Fujifilm X-T30
    • Phone
  • 03

    Travel

    • New cities
    • Concert trips
  • 04

    Sport

    • Tennis
    • Padel
    • Football
    • Formula 1

Shot by me

  • Bay of Kotor at dusk, seen from the hills above the old town
    Kotor
  • A woman on a bench next to a street lamp, city skyline at sunset
    Novi Sad
  • View from Petrovaradin Fortress over the Danube in golden light
    Novi Sad
  • Two silhouettes watching the sun set over the city
    Novi Sad
  • Genex Tower framed by trees
    Belgrade

Hiring? Let’s talk.

Email is the fastest way to reach me. The resume has the full story.

Copy emailResume

My work

Websites for Space307 and Place.01, plus a Next.js archive of every concert I’ve been to.

Selected work · 03

My work

  • Space307

    space307.com

    Website for Space307, the international fintech product company I worked at. Available in English and Greek.

    • React
    • TypeScript
    • Vite
    • Motion
    • i18n

  • Place.01

    place01.ru

    Company website for Place.01, a fintech development studio.

    • React
    • TypeScript
    • Vite
    • Motion

  • Concerts Archive

    My log of every concert I’ve been to, with a map of everywhere I’ve seen live music.

    • Next.js
    • React
    • TypeScript

Hiring? Let’s talk.

Email is the fastest way to reach me. The resume has the full story.

Copy emailResume

Approach

How I build

Simple code over clever code, TypeScript everywhere, state kept next to where it’s used and speed checked from the first commit.

Approach · 04 principles

How I build

  1. 01

    Readable over clever

    Someone will read this code after me, often me a year later. Clear names and small components help them more than smart tricks.

  2. 02

    Typed end to end

    TypeScript from the API layer to the UI, so the compiler catches most of what a refactor breaks.

  3. 03

    State where it belongs

    Server state in React Query, UI state next to the component that uses it, a global store only when it pays off.

  4. 04

    Fast from day one

    I set a performance budget and watch Core Web Vitals from the first commit. Speeding a site up the week before release is always harder.

Stack

Tools I ship with

  • React
  • TypeScript
  • Next.js
  • Astro
  • Zustand
  • MobX
  • React Query
  • Vite
  • Node.js
  • Jest
  • Figma
  • Tailwind

Stack · 12 tools

Tools I ship with

Core

  • React
  • TypeScript
  • Next.js
  • Astro

State & data

  • Zustand
  • MobX
  • React Query

Tooling

  • Vite
  • Node.js
  • Jest
  • Figma

Styling

  • Tailwind