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Serhii Kovalov

@serhiikovalov

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Full-stack developer specializing in scalable SaaS and blockchain e-commerce solutions.

France

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What I'm looking for

I seek a role building scalable, production-ready SaaS or Web3 systems where I can lead architecture, improve reliability, and mentor engineers.

I am a full-stack software developer with over 8 years of hands-on experience building scalable SaaS and blockchain e-commerce products using JavaScript, Python, and Go. I design and implement robust back-end and front-end systems, migrate monoliths to microservices, and build event-driven architectures that handle massive data flows.

My work spans startups and agencies where I shipped high-throughput web applications, improved test coverage by 70%, and led teams to enhance performance and reliability—achieving threefold performance improvements and 99.99% uptime for legacy platforms.

I have experience with AWS, S3-compatible and Web3 storage, Stripe billing integrations, TDD, and mentoring developers. I focus on delivering production-ready features, secure APIs, and architectures that scale for enterprise usage.

Experience

Work history, roles, and key accomplishments

Full-Stack Engineer

Skello

Dec 2024 - Jul 2025 (7 months)

Owned back-end and front-end development, led migration from a monolith to microservices, and built event-driven solutions (Kinesis, SQS) on AWS to handle massive data loads.

AWS Event Driven Architecture Microservices Kinesis SQS JavaScript Python

Co-Founder

LearnLenny

Jul 2023 - Dec 2024 (1 year 5 months)

Built and maintained back-end and front-end of an AI learning platform, delivering core features and platform stability during product development.

Python JavaScript Web Development SaaS

Full-Stack Engineer

Outsight.ai

Oct 2023 - Nov 2024 (1 year 1 month)

Delivered web features for high-volume spatial surveillance applications, applied TDD and event-driven patterns to process massive people-flow data reliably.

TDD Event Driven Architecture Python JavaScript Web Applications LiDAR

Back-End Engineer

Coldstack/Petabox

Nov 2021 - Jul 2023 (1 year 8 months)

Developed secure web APIs and S3-compatible Web3 storage features, maintained finance modules (billing via Stripe and Web3) and contributed to product architecture.

Web3 API Development AWS S3 Stripe & Security Architecture

Full-Stack Engineer

JetRuby Agency

May 2019 - Sep 2021 (2 years 4 months)

Supported and developed e-commerce SaaS products, improved performance and reliability (3x performance gain, 99.99% uptime) and mentored junior developers while leading a team of three.

TypeScript React Vue.Js PostgreSQL Performance Optimization Mentoring E Commerce Ecommerce

Full-Stack Engineer

Constant Solutions

Jan 2017 - Apr 2019 (2 years 3 months)

Built and maintained modules for cryptocurrency exchange solutions, focusing on communication modules (chats, WebSockets, bots) and internal CRM integrations.