Denys

Denys Diachenko
Senior Full-Stack Developer
8 Years Experience
Intermediate English Level

Professional Summary
Senior Full-Stack Developer with 8+ years of commercial experience building web, mobile, and high-volume
e-commerce products. Strong frontend expertise in React, Next.js, and React Native, complemented by
hands-on backend experience with Laravel, Node.js, MySQL, Redis, Elasticsearch, queues, and third-party
integrations. Designed a multichannel commerce platform managing approximately 3 million listings and
close to 1 million unique SKUs, and led a team of three junior developers through architecture decisions,
estimation, code reviews, and onboarding. Uses AI-assisted engineering tools to accelerate implementation,
testing, debugging, and refactoring while maintaining human review and production-quality validation.

Tech Skills

JavaScript TypeScript React Next.js React Native

Redux toolk- Laravel MySQL PostgreSQL RESTful APIs
it

Secondary Skills
Websocket Node.js Redux saga TailwindCSS SASS/LESS Ant Design

Supabase Redis Elasticsearch Stripe PayPal Twilio API Ebay

Docker AWS CI/CD Pipelines Jest Eslint Sentry Rollbar

Claude.ai Cursor Codex

Key Achievements

Proficiency in Software Development

- Delivered full-cycle web and mobile development, from requirements analysis and architecture
decisions to implementation, testing, deployment, monitoring, and production support.
- Designed maintainable full-stack solutions using React, Next.js, React Native, Laravel, Node.js,
relational databases, queues, and third-party APIs.
- Built high-volume data-processing and integration workflows involving marketplace listings,
supplier inventory, pricing, orders, payments, and real-time communication.
- Applied AI-assisted development workflows to accelerate implementation, testing, debugging, and
refactoring while retaining human review and production-quality validation.

Collaborative Creativity

- Worked directly with clients and cross-functional teams to translate business requirements into
practical technical solutions.
- Participated in architecture discussions, clarified technical trade-offs, estimated implementation
effort, and communicated delivery risks.
- Collaborated with designers, backend developers, QA engineers, and stakeholders to deliver
consistent web and mobile experiences.
- Contributed technical suggestions beyond assigned tasks, helping simplify workflows, identify edge
cases, and improve product maintainability.

Technical Guidance and Mentorship

- Led a team of three junior developers for approximately one year, taking responsibility
for task distribution, estimation, architectural guidance, code reviews, onboarding, and client
communication.
- Conducted regular code reviews focused not only on identifying issues but also on explaining
trade-offs, alternative approaches, and maintainability concerns.
- Introduced monthly JavaScript problem-solving sessions where developers explored multiple
correct solutions to the same task, strengthening their understanding of core language features and
problem-solving techniques.
- Helped all three junior developers progress to commercial client projects within approximately six
months, where they successfully joined delivery teams.

Enhancement of Performance and Scalability

- Designed asynchronous, queue-based workflows for a multichannel platform managing
approximately 3 million listings and close to 1 million unique SKUs.
- Optimized supplier inventory synchronization through incremental four-hour updates where
supported and scheduled FTP-based catalog imports for other suppliers.
- Used MySQL as the transactional source of truth and Elasticsearch as a dedicated search engine,
balancing data consistency with fast catalog search.
- Implemented centralized logging and Telegram/email alerts for failures in business-critical
synchronization, pricing, and order-processing workflows.
- Built server-rendered service and location pages with Next.js and optimized them to achieve green
PageSpeed Insights scores.

Certifications
Claude Code in Action Certificate

JUL, 2026

Building with the Claude API Certificate

JUL, 2026

Model Context Protocol: Advanced Topics Certificate

JUL, 2026

Foundational C# with Microsoft Certificate

Foundational C# with Microsoft — freeCodeCamp
DEC, 2024 - DEC, 2025

Education
Master's degree

Engineering Mechanics | Ukrainian National Central University
SEP, 2009 - SEP, 2014

Last Projects Engaged
Full-Stack Developer | Multichannel Automotive E-commerce Platform

Developed a high-volume automotive e-commerce and back-office platform integrating three eBay
accounts, two Amazon accounts, a proprietary online store, and seven automotive parts suppliers.
Technologies
Laravel, React, MySQL, Elasticsearch, Redis, queues, cron workers, Guzzle, eBay API, Amazon API, supplier
APIs, FTP, XML/CSV

Features
• Designed and developed a multichannel platform managing approximately 3 million listings across eBay, Ama-
zon, and the company’s online store, representing close to 1 million unique SKUs.

• Built order-processing workflows handling approximately 50–100 orders per day. Supplier integrations and
conditional automatic ordering enabled the complete operation to be managed by only one or two employees.

• Integrated seven automotive parts suppliers, normalizing different APIs, data formats, authentication mecha-
nisms, and ordering workflows behind a consistent internal interface.

• Implemented inventory synchronization that refreshed supplier availability five times per day for each SKU and
propagated stock changes across all connected sales channels.

• Designed an incremental synchronization flow for a supplier that exposed inventory changes by time range,
retrieving four-hour change sets instead of repeatedly importing the complete catalog.

• Built FTP-based ingestion pipelines for suppliers that published complete inventory files, including downloading,
parsing, validating, and storing large supplier datasets.

• Developed configurable pricing formulas based on supplier cost, core cost, marketplace fees, sale rates, and
other business parameters, automatically recalculating prices whenever SKU data changed.

• Added price-safety validation that compared newly calculated prices with the last accepted price and blocked
marketplace updates when the difference exceeded 20%, assigning the listing a warning status for manual review.

• Implemented centralized request and error logging, together with Telegram and email alerts for failures in
business-critical synchronization and order-processing workflows.

• Revised an early architectural decision to use Elasticsearch as the primary datastore. Migrated the system of
record to MySQL and retained Elasticsearch as a dedicated search engine, improving data consistency while
preserving fast catalog search.

APR, 2015 - AUG, 2021

Part-Time Full-Stack Developer | Multichannel Automotive E-commerce Platform

-
Technologies
React, Laravel, Redux

Features
• Continued supporting and developing the platform on a part-time basis after joining Onix.
• Helped separate part of the existing system into a new standalone application positioned as an automotive parts
supplier.

• Designed and implemented the architecture of the new application using React, Redux, and Laravel.
• Reused and adapted existing product-domain knowledge while establishing a separate codebase and application
architecture.

• Supported the gradual transition from the original multichannel system to the new supplier-focused product.

CrewForge HQ

Technologies
Next.js, TypeScript, Supabase, Twilio, Stripe, Google Analytics, Vercel

Features
• Designed business onboarding, lead management, analytics, payments, and AI-assisted SEO content-generation
workflows.

• Implemented server-side rendering for dynamically generated service and location pages and optimized them
to achieve
green PageSpeed Insights scores.

• Integrated Twilio voice and SMS lead capture, Stripe payments, and Supabase-backed application data

JAN, 2026 - JUL, 2026

Project Under NDA

Technologies
Next.js, TypeScript, Stripe, WebSockets, Ant Design, Segment

Features
• Built real-time messaging with typing indicators, read receipts, presence status, and notifications using WebSock-
ets

• Developed workflows spanning projects, proposals, offers, milestones, attachments, reviews, and AI-assisted
matching.

• Implemented Stripe card payments, invoices, milestone releases, failure states, and transaction history.

APR, 2024 - APR, 2025

Project Under NDA

Technologies
React Native, Redux Toolkit, Terra SDK, Twilio, Rollbar, App Center

Features
• Owned end-to-end development of the application's main social feed, delivering an Instagram-style content
experience as
one of the product's core user workflows.

• Set up shared ESLint standards, automated iOS and Android builds in App Center, and Rollbar production
monitoring.

• Integrated Terra SDK for wearable-device data and Twilio for OTP verification, reminders, and SMS notifications

SEP, 2021 - NOV, 2022

Project Under NDA

Technologies
React, React Native, Redux, Redux Saga, Stripe, PayPal, Sentry

Features
• Contributed to React web and React Native mobile applications for workout tracking, personalized programs,
subscriptions,
and coach communication.

• Integrated Sentry, Stripe, PayPal, in-app purchases, and Google authentication across web and mobile.

JAN, 2021 - JAN, 2023