Сергiй

SERHII KALITIN
Full Stack Developer (Node.js | Nest | React | Next.js | PHP | WordPress)
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SUMMARY

Fullstack Developer with 8 years of experience building scalable, high-performance applications using TypeScript, Node.js,
NestJS, React, Next.js, PHP, and WordPress. Specialized in developing high-load and data-intensive systems capable of handling
large volumes of traffic with high reliability and efficiency.

Strong background in PHP and WordPress, having developed numerous production websites, custom themes, plugins, and REST
API integrations. Experienced in optimizing WordPress for performance, caching, security, and SEO, as well as creating bespoke
functionality for complex business requirements.

Proficient in modern frontend development using React and Next.js, including SSR, SSG, ISR, advanced state management,
component architecture, and integrating frontend applications with REST/GraphQL backends. Delivered multiple responsive,
SEO-friendly, and highly interactive interfaces for both marketing websites and full web applications.

Experienced in building data-driven backend systems with NestJS and microservice architectures. Skilled in designing traffic
analytics tools, including real-time click tracking, event validation, and conversion reporting.

Well-versed in SQL and NoSQL databases (MySQL, PostgreSQL, MongoDB, Redis), with strong expertise in schema design,
indexing, and query optimization. Integrated AWS services (S3, Lambda) for efficient media processing and built Kafka-based
pipelines for asynchronous event logging and analytics.

Collaborated closely with frontend, product, and DevOps teams to deliver secure, test-covered, CI/CD-ready solutions with a
strong emphasis on backend performance, observability, clean architecture, and long-term maintainability.

EMPLOYMENT HISTORY

Fullstack Developer (PHP + WordPress / React / Node.js) Oct 2021 - Nov 2025
freelance projects

cerealzavod.com
Developed a WordPress-based website using custom PHP solutions and ACF. Implemented pixel-perfect layout from Figma
and built several custom features tailored to client requirements.

navigart.info
Created a full WordPress solution with PHP and ACF, including layout implementation, content setup, and a fully custom
contact form with backend processing.

barber.topsmm.kiev.ua
Developed backend API in PHP and integrated it with a React frontend. Built the data exchange logic and handled
communication between frontend components and the backend system.

103taxi.com
Developed a WordPress-based website using custom PHP solutions and ACF. Implemented pixel-perfect layout from Figma
and built several custom features tailored to client requirements.

ceflab.com
Developed backend API in PHP and integrated it with a React frontend. Built the data exchange logic and handled
communication between frontend components and the backend system.
sacura.ua
Implemented a complete layout from Figma and developed a custom WordPress theme from scratch using PHP and ACF.
Delivered a fully responsive website with tailored functionality and content structure.

topsmm.kiev.ua
Developed a custom WordPress website using PHP and ACF. Implemented a pixel-perfect layout based on Figma designs
and built responsive sections with dynamic content. Integrated custom features tailored to client needs, including interactive
elements and optimized content structure.

roinstyle.it
Created a WordPress website from scratch with PHP and ACF, following Figma layouts precisely. Delivered a fully responsive
design with dynamic content and custom functionalities tailored to client requirements.

lezhepekova.com
Developed a custom PHP solution integrating the WayPay payment system. Built a fully custom orders page displaying paid
transactions with dynamic content management. Implemented backend logic to handle payments, order tracking, and user
interaction efficiently.

hospice-life.com.ua
Built a complete WordPress website from scratch, including theme development and layout implementation. Converted
Figma designs into a responsive, pixel-perfect layout and set up all content using custom fields (ACF). Developed custom
functionality and interactive sections tailored to client needs, delivering a fully functional and easily manageable site.

idea.topsmm.kiev.ua
Developed a complete WordPress website from scratch, including custom theme creation and responsive layout
implementation. Used PHP and ACF to structure dynamic content and built custom functionality tailored to the project’s
goals. Delivered a clean, fast, and fully manageable site.

betwixtgroup.com
Created a fully custom WordPress solution with a hand-coded theme, PHP backend logic, and ACF integration. Implemented
a clean and responsive layout from design files and built dynamic content sections and custom features for seamless content
management.

treeoflife-amt.com.ua
Built a full WordPress website from the ground up, including theme development, layout integration, and custom PHP
functionality. Implemented ACF-based content management and delivered a responsive, well-structured website optimized
for usability and client needs.

Fullstack Developer Dec 2018 - Aug 2021
PoltavaGas Office

Developed the official Poltava Gas corporate website as the lead and sole developer, building the entire platform from scratch
using WordPress and custom PHP development.

Delivered a fully functional production-ready system, including:
– Custom online payment module for utility bills.
– Meter reading submission functionality with validation and user history tracking.
– Accessibility-friendly theme designed specifically for users with visual impairments, following WCAG best practices.
– User authentication system with registration, login, and personal account features.
– News and content management modules for company-wide announcements and updates.
– Responsive, mobile-optimized UI aligned with branding and the requirements of company management.

Implemented a fully custom WordPress theme with optimized performance, advanced caching, and security hardening.
Integrated multiple APIs and created tailored admin tools to streamline content and user management.

Successfully delivered a complete end-to-end solution meeting all business, design, and accessibility requirements.
Additionally, deployed the project to production, configured hosting infrastructure, caching layers, and monitoring tools.
Provided long-term maintenance, updates, bug fixes, performance optimization, and feature improvements to ensure the
system remained stable and secure in daily operation.
 SKILLS

Languages: JavaScript, TypeScript, PHP.
Backend: Node.js, Express, Fastify, NestJS, PHP (WordPress).
Frontend: React, Redux, Tailwind, Next.js, HTML5, CSS3, SASS, SCSS
Databases: PostgreSQL, MySQL, SQLite, MongoDB, Redis, ClickHouse, Supabase
ORM / ODM: TypeORM, Sequelize, Prisma, Mongoose
APIs & Protocols: REST, GraphQL, WebSockets, JWT, OAuth, HTTP
Documentation: OpenAPI, Swagger
Messaging / Queues: RabbitMQ, Kafka
Cloud & DevOps: Docker, AWS S3, AWS Lambda, CI/CD
Version Control: Git, GitHub, GitLab, BitBucket
Testing: Jest, Mocha
Payments: Stripe

EDUCATION

Bachelor Degree Sep 2018 - Jun 2022
National University "Yuri Kondratyuk Poltava Polytechnic"

LANGUAGES

English (Intermediate), Ukrainian (Native).