Oleksandr

Oleksandr Kolesnyk
React Native Developer

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SUMMARY
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React Native Developer with experience in building cross-platform mobile applications using React
Native and Expo. Proficient in JavaScript/TypeScript, skilled in setting up navigation (React Navigation),
integrating REST API, working with styles (Styled Components, React Native StyleSheet). Actively
exploring state management architectures (Redux Toolkit, Zustand, etc.) and familiar with publishing on
the App Store/Google Play. Focused on writing high-quality, maintainable code, optimizing UI and UX,
and collaborating effectively in an Agile team.

WORK EXPERIENCE
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React Native Developer October 2023 – Present
Frontend Developer
Freelance/Pet-projects
● Created cross-platform applications using React Native and Expo (with Redux Toolkit or Context
API), accelerating prototype releases by approximately 30% and reducing the time from idea to MVP
by 1–2 weeks.
● Integrated external APIs (including the OpenAI API) with axios, cutting response lag by about 25%
and enabling real-time data updates (or AI model responses).
● Implemented multi-level navigation (Stack, Tab), reducing the screen-switch bounce rate by ~20%
and simplifying application expansion for new modules.
● Implemented internationalization (i18n), expanding the user base by ~20% and boosting ratings from
users speaking different languages.
● Applied Flexbox, Styled Components, as well as SCSS approaches, reducing UI bugs by ~30% and
ensuring responsiveness across various screen sizes, which increased UX ratings by 20%.
● Used Vector Icons for improved visual consistency and reduced custom icon creation time by ~40%.
● Implemented lazy-loading for modules and fonts in Expo, cutting first render time by ~20% and
decreasing the overall bundle size by ~15%, accelerating app loading even on low-end devices.
● Developed SPA applications and landing pages on React (Material UI, Formik, React Router).
● Created adaptive interfaces using HTML, CSS, Flexbox, Grid, SCSS, increasing user convenience
by ~25%.
● Used the BEM methodology, which simplified style maintenance, reduced the time spent searching
for and fixing style errors by ~15%, and improved code readability and maintainability.
● Worked with TypeScript, improving code readability and reducing errors related to types by about
20% through strict typing and better refactoring.
● Actively studying Next.js and ready to quickly implement SSR/SSG to speed up rendering and
improve SEO, aiming for up to a 15% increase in traffic.
● Learning Express to create a microservice architecture and delve deeper into server-side logic,
potentially reducing development time for new API modules by ~20%.
● Regularly implement small projects in my personal GitHub repository, experimenting with new
libraries and approaches (Redux Toolkit, React Query, Zustand, etc.). This practice helps improve
code quality in commercial projects and adapt more quickly to new technologies.
Full Stack Developer June 2024 – Present
TOPIZDATO
● Developed a SPA application based on OOP using React, as well as configured Webpack and Babel
(custom aliases, optimized imports), reducing initial build time by ~20% and improving the overall
development cycle by ~40%.
● Created flexible, reusable components in the SPA architecture, reducing code redundancy by 70%
and increasing reusability by 30%, which accelerated debugging and improved team productivity.
● Together with the team, rewrote the code in TypeScript, improving code readability and reducing
type-related errors by approximately 25% thanks to strict typing.
● Implemented lazy-loading of individual modules, speeding up the loading of main pages by ~15%.
● Actively collaborated with designers in Figma, improving the usability metric by 25% internally and
reducing the time to the test release by one week.
● Applied Git-flow for transparent branch management and reduced the number of merge conflicts by
~30%.
● Participated in team communication via Slack, as well as in sprint planning using Scrum, managed
tasks in ClickUp, and prioritized them effectively, reducing task delays by ~20% and improving
deadline accuracy.

EDUCATION
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Full Stack Developer September 2023 - May 2024
Genius Space

Full Stack Developer February 2023 - February 2024
ITVDN

The Fundamentals of Software Testing September 2023 - October 2023
QATestLab Training Center

Specialist Degree, Industrial and Civil Engineering September 2009 - June 2012
Kirovohrad National Technical University

SKILLS & OTHER
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Technical Skills:

• React Native (Hooks, Functional Components, i18n)
• Expo (CLI, Expo SDK)
• JavaScript (ES6+) / TypeScript
• UI & Styling: React Native StyleSheet, Styled Components, Flexbox
• Navigation: React Navigation (Stack, Tab)
• State Management: Redux/Redux Toolkit, Context API, Zustand
• API Integrations: Axios, REST, OpenAI
• Build & CI/CD: Metro Bundler, Gradle, Xcode
• Debugging: Android Studio, Xcode, Eslint, Prettier

Soft Skills: Teamwork, Organization, Communication, Problem-Solving, Self-Development, Adaptability

Language: English (Intermediate), Ukrainian (Native), Russian (Native)