Valerii

Valerii Demidov — Senior Software Engineer
React • TypeScript • Node.js • Next.js • System Design

Cherkasy, Ukraine, [open contact info](look above in the "contact info" section), [open contact info](look above in the "contact info" section)

LINKS Telegram, LinkedIn

PROFILE Senior Software Engineer with 7+ years building production web apps end-to-end: React/TypeScript
frontends, Node.js/Next.js services, and cloud-first deployments (Vercel/AWS/Firebase). I’ve led teams,
designed component systems, optimized performance, and integrated complex APIs and third-party
services. I want to grow in the IT sphere to be a better engineer. Have more impact to the team, projects,
and business.

EMPLOYMENT HISTORY

Feb 2025 — Present Senior Frontend Developer, 5874 Commerce
●​ Built and customized React/TypeScript features on large production apps; improved UX and
conversion.
●​ Implemented Next.js/Catalyst changes for headless frontends; shipped fixes across multiple
repos.
●​ Designed and delivered Node.js integrations and automated flows around checkout, refunds,
and marketing APIs.
●​ Owned API/SDK usage patterns and error-handling standards for reliability across projects.​

Nov 2023 — Jan 2025 Senior Frontend Developer, Space48
●​ Delivered new React features and performance improvements on complex storefronts and
internal tools.
●​ Integrated advanced search/merchandising, asset, and analytics platforms; standardized data
contracts.
●​ Led client demos and technical discovery; translated product goals into actionable engineering
plans.
●​ Customized checkout flows and payment logic with robust validation, observability, and
rollback paths.​
​
Tech: React, TypeScript, Node.js, Next.js, GTM, API integrations, Storybook​

Apr 2023 — Oct 2023 Lead Bigcommerce Developer, Onacy
●​ Led implementation of React features and Node.js services; introduced component library and
UI guidelines.
●​ Built serverless functions and Firestore models; added observability and error budgets.
●​ Prototyped AI-assisted workflows via ChatGPT API to accelerate content and support tooling.​
​
Tech: React, Next.js, Node.js, Firebase Functions, Firestore, ChatGPT API​

Jun 2021 — Mar 2023 Head of the Bigcommerce department, Soft-Loft
●​ Grew and led an 8-engineer team; defined code standards, review process, and CI gates.
●​ Introduced React to legacy stacks; guided architecture for headless frontends and modular
services.
●​ Established partner relations and technical discovery practices; unblocked complex
integrations.​
​
Tech: React, Next.js, Node.js, APIs, CI/CD​
Oct 2020 — Jul 2021 E-commerce developer, Codifi
Created online stores using the Bigcommerce platform and started a new studying platform for teaching
new developers the Bigcommerce platform. Customization Bigcommerce checkout. Site speed
optimization.
Technologies: Stencil, Bigcommerce, node.js, Vue.js, React, Bigcommerce API ​

Mar 2019 — Present Magician, Upwork / E-commerce / finten.space
●​ Creating online stores using Bigcommerce and Shopify
●​ E-commerce applications creation
●​ Headless
●​ App integration
Technologies: Stencil, bigcommerce, Shopify, node.js, React, Angular, AWS, Firebase, Vercel,
DigitalOcean ​

Jun 2017 — Jul 2019 Full stack web developer, Skyservice
●​ Developed online store functionalities including cart integration and user checkout processes.
●​ Implemented delivery profiles and refined catalog filters to enhance user experience.
●​ Conducted bug fixes to ensure seamless operation of web applications.
●​ Utilized technologies such as Node.js, Angular, and MongoDB to deliver robust e-commerce
solutions.
Mar 2015 — Apr 2017 System Administrator, Volodymyr Vynnychenko
State Pedagogical University
●​ Network management and monitoring.
●​ Hardware welfare support.
Technologies: Linux servers, Zabbix, PHPVirtualBox, Mail server, LDAP

EDUCATION

Jan 2015 — Jan 2016 Computer Science course, SHPP (programming.kr.ua)
programming school
Jan 2011 — Jan 2017 Master of Science degree, Kirovohrad State Pedagogical
University, named after V.Vynnychenko

SKILLS Frontend: I build scalable React and TypeScript applications, mostly with Next.js. I enjoy creating
clean, reusable component systems and working with Storybook to keep everything consistent.
Backend: I work with Node.js and serverless APIs (Firebase, Express). I’ve designed and integrated
REST and GraphQL endpoints for various projects, focusing on reliability and clarity.
Architecture & Quality: I care a lot about code structure, readability, and performance. I usually set
up CI/CD pipelines, write unit tests, and automate deployments to keep things smooth and
predictable.
Data & Cloud: I’ve worked with MongoDB, MySQL, and Firestore, and usually deploy apps to
Vercel or AWS depending on the project setup.
Ecosystem & Workflow: I’m comfortable with Git-based collaboration, agile workflows, and
handing off designs from Figma. I enjoy API-driven development and building tools that help teams
move faster.

LANGUAGES English B2 Ukrainian Native speaker