Serguei is available for hire
Hire SergueiSerguei Nevarko
Verified Expert in Engineering
Software Developer
Montreal, QC, Canada
Toptal member since May 10, 2022
Bio
Serguei specializes in code architecture, React efficiency, and back-end flexibility. The more complex and interactive the app, the more he will shine. He has built many web applications from the ground up while working as a freelancer and communicates well with clients. By being used to constantly learning new things, Serguei will always be able to adapt to any requirements or propose new and better ways to structure the application.
Portfolio
Checkflo
PHP, MySQL, JavaScript, HTML, CSS, APIs, HTML5, Full-stack, API Integration...
Juniper Learning Design Corp.
JavaScript, TypeScript, Node.js, API Integration, REST APIs, Back-end, HTML...
Progamma
JavaScript, Node.js, ChatGPT, OpenAI, ChatGPT API, Botpress.io, UI Development...
Experience
- HTML - 14 years
- JavaScript - 14 years
- MySQL - 10 years
- CSS - 7 years
- APIs - 6 years
- React - 6 years
- Node.js - 6 years
- MongoDB - 6 years
Work Experience
Software Developer
2012 - PRESENT
Checkflo
- Developed the software that allows clients to log in with QuickBooks and import their check information into our software. The next business day, they are generated, printed with the appropriate shipping labels, and sent out by the company.
- Developed RESTful APIs for our clients so that they can upload batches of checks to print out.
- Integrated modules using various APIs like Versapay, Endicia, USPS, QuickBooks, and Twilio.
Technologies: PHP, MySQL, JavaScript, HTML, CSS, APIs, HTML5, Full-stack, API Integration, Architecture, Database Modeling, REST APIs, Technical Architecture, Front-end Development, ECMAScript (ES6), REST, CSS3, Vanilla JS, Back-end Architecture, User Experience (UX), User Interface (UI), SQL, Software Architecture, Full-stack Development, Web App Development, Reports, Dashboards, Twilio, Payment APIs, Responsive Web Apps, Postman, Single Sign-on (SSO), UI Design, UX Design, UI Development, Technical Leadership, Git, Authentication, Authorization, Relational Databases, Data Modeling, Software as a Service (SaaS), Solution Architecture, Single-page Applications (SPAs), Integration, Agentic AI, Web Applications, RESTFul APIs, API Architecture, Back-end Development, API Design, API Testing
Full-stack Node.js Developer
2025 - 2025
Juniper Learning Design Corp.
- Developed a "low code/no code" framework for facilitating the creation of new AI flows with ChatGPT and managing the app's logic.
- Created an AI that evaluates and grades written assignments of students based on the teachers' requirements.
- Developed the entire application from scratch and deployed everything online. That app was then inserted into the Rise Articulate 360 platform, and students were able to use my component in lessons.
Technologies: JavaScript, TypeScript, Node.js, API Integration, REST APIs, Back-end, HTML, CSS, OpenAI API, ChatGPT, MongoDB Atlas, GitHub, Technical Leadership, Git, Authentication, Solution Architecture, Single-page Applications (SPAs), PostgreSQL, Integration, Web Applications, RESTFul APIs, API Architecture, Back-end Development, API Design, API Testing
Software Developer
2024 - 2025
Progamma
- Developed a chatbot with Botpress that answers questions based on the rules and guidelines of Health Canada, WHO, FDA, and EMA.
- Created a RAG from scratch with my own embeddings and ChatGPT API to answer user questions since Botpress wasn't good enough to give us enough control.
- Developed the entire application from scratch (MVP of the project), which includes the front and back end, with deployment online.
Technologies: JavaScript, Node.js, ChatGPT, OpenAI, ChatGPT API, Botpress.io, UI Development, Vite, Artificial Intelligence (AI), TypeScript, MongoDB Atlas, GitHub, Technical Leadership, Git, Authentication, Solution Architecture, Large Language Models (LLMs), Single-page Applications (SPAs), Web Applications, RESTFul APIs, API Architecture, Back-end Development, API Design
Senior Full-stack Developer
2024 - 2024
Code Particle Inc.
- Fixed software bugs and UI issues on both the front and back end.
- Worked on automation to test the application when a new version was released.
- Added new features to the application when required.
- Helped with updating the Next.js app to the newer version with the new folder structure.
Technologies: React, Node.js, JavaScript, Full-stack, APIs, HTML, Next.js, Headless CMS, Shopify API, Playwright, UI Design, UX Design, UI Development, Git, Authentication, Automated Testing, CI/CD Pipelines, Artificial Intelligence (AI), Solution Architecture, Web Applications, Browser Automation, RESTFul APIs, API Architecture, Back-end Development, API Design
Full-stack Developer
2023 - 2023
Crockpot Enterprises LLC
- Built a responsive web application from scratch for a lottery number generator in React and Node.js and deployed everything online.
- Made a custom calibration section on the website so clients get results uniquely calibrated to their printers at home.
- Made an admin page to control website features and create guest accounts.
Technologies: Full-stack Development, JavaScript, HTML, CSS, Algorithms, Node.js, Tailwind CSS, Styled-components, React, Heroku, MongoDB, Express.js, PayPal, Mobile First, Web App Development, MERN Stack, Payment APIs, Responsive Web Apps, UI Design, UX Design, UI Development, MongoDB Atlas, GitHub, Technical Leadership, Git, Authentication, Web Applications, RESTFul APIs, Back-end Development, API Design
Full-stack Developer
2023 - 2023
Toronto Boutique Apartments
- Used the Guesty API to fetch all relevant data about properties and remade their entire front-end website from scratch.
- Integrated Stripe to process payments on a very specific payment schedule.
- Created several reusable and efficient components in React to facilitate project development.
- Integrated Postmark API to be able to send emails to customers.
- Did weekly deployments online and calls with the client for a smooth development cycle.
Technologies: Node.js, React, Google Maps API, REST APIs, Stripe API, Styled-components, CSS, UI Components, Web UX Design, Front-end Development, ECMAScript (ES6), REST, Responsive Web Design (RWD), CSS3, Stripe, Back-end Architecture, Minimum Viable Product (MVP), User Experience (UX), User Interface (UI), Software Architecture, Full-stack Development, Mobile First, Web App Development, MERN Stack, Socket.IO, Twilio, Payment APIs, Responsive Web Apps, Postman, UI Design, UX Design, UI Development, TypeScript, MongoDB Atlas, GitHub, Technical Leadership, NestJS, Git, Authentication, Authorization, Relational Databases, Data Modeling, Solution Architecture, Single-page Applications (SPAs), Integration, Web Applications, RESTFul APIs, API Architecture, Back-end Development, API Design, API Testing
Senior Full-stack Developer
2022 - 2022
Whistlaw
- Developed a whistleblower system to help European companies conform to the new EU regulations.
- Wore multiple hats to develop the software to allow whistleblowers to submit fraudulent/illegal activities anonymously, having organization handlers to manage these cases and admins to track the overall progress with charts.
- Built custom charts, modern-looking dashboards, filterable tables, notification system, and PDF generation.
- Created an advanced subscription module with different prices using Stripe API.
- Implemented different APIs: Dropbox, Stripe, and Postmark.
- Recreated Figma designs in React that the client provided.
Technologies: Node.js, React, Charts, Back-end, CSS, APIs, Full-stack, API Integration, Architecture, Database Modeling, REST APIs, Stripe API, Startups, Technical Architecture, Leadership, Front-end Development, ECMAScript (ES6), REST, CSS3, Stripe, Back-end Architecture, Minimum Viable Product (MVP), User Experience (UX), User Interface (UI), Software Architecture, Full-stack Development, Web App Development, MERN Stack, Reports, Dashboards, Payment APIs, UI Design, UX Design, UI Development, MongoDB Atlas, GitHub, Technical Leadership, Git, Authentication, Authorization, Data Modeling, Solution Architecture, Single-page Applications (SPAs), Web Applications, RESTFul APIs, API Architecture, Back-end Development, API Design
Front-end Developer
2022 - 2022
Bassam Abdellatif
- Developed an app that manages real-estate rentals between property managers, landlords, and tenants.
- Created a multi-login with different accounts and dashboards. Each account type has its own set of pages and permissions.
- Set up several APIs (Google Maps, Stripe, file management, etc.) to fit project requirements.
Technologies: HTML, JavaScript, CSS, Front-end, APIs, React, Node.js, Google Maps, Dropbox API, Live Chat, Cloud Storage, Redux, API Integration, Architecture, Database Modeling, REST APIs, Stripe API, Startups, Technical Architecture, Leadership, Front-end Development, ECMAScript (ES6), REST, CSS3, Stripe, Back-end Architecture, Minimum Viable Product (MVP), User Experience (UX), User Interface (UI), Software Architecture, Full-stack Development, Web App Development, MERN Stack, Socket.IO, Payment APIs, eCommerce, UI Design, UX Design, UI Development, MongoDB Atlas, GitHub, Technical Leadership, Git, Authentication, Authorization, Data Modeling, Single-page Applications (SPAs), Web Applications, RESTFul APIs, API Architecture, Back-end Development, API Design
Software Developer
2013 - 2019
9277-0759 Quebec Inc.
- Developed a desktop application using Windows Forms. Since there were many screens, each one was built as a .dll file and dynamically imported into a custom tab control to have multiple windows at once.
- Created various custom controls for the user interface.
- Developed a customized mailing module using the SMTPS protocol. The one provided by default did not have the option for a bounce address, so it had to be implemented manually.
Technologies: C#, Windows Forms (WinForms), Front-end, Back-end, Web Development, Technical Architecture, Responsive Web Design (RWD), User Experience (UX), .NET
Project History
Systematic Organic Results (SOR)
https://sor-seo.com/A B2B service for filtering out a vast amount of people on LinkedIn to extract high-value prospects. We then systematically connect and organically engage with them to book calls and meetings for our clients.
Since other businesses are in the market about 5% of the time, after our campaign ends, the client is left with a powerful network of people they can follow up with in the future, either by message or phone call.
Since other businesses are in the market about 5% of the time, after our campaign ends, the client is left with a powerful network of people they can follow up with in the future, either by message or phone call.
Code Farm Online | Programming Course
This is a new project, and only the MVP was launched. It is an online programming course that is very interactive and flexible. It can branch out based on answers to better help the students, and there are mini-games to solve using code at the end of lessons.
Education
2013 - 2017
Bachelor's Degree in Computer Science
McGill University - Montreal, QC, Canada
Skills
Libraries/APIs
Node.js, React, REST APIs, Stripe, Stripe API, Socket.IO, Puppeteer, Windows Forms (WinForms), Google Maps, Dropbox API, Google Maps API, Shopify API, Playwright, OpenAI API
Tools
Git, MongoDB Atlas, Figma, GitHub, Postman, ChatGPT
Languages
JavaScript, PHP, HTML, CSS, HTML5, ECMAScript (ES6), SCSS, TypeScript, CSS3, SQL, C#, Python, Java
Frameworks
Express.js, Redux, Vanilla JS, Tailwind CSS, Botpress.io, Next.js, .NET, React Native, NestJS
Paradigms
REST, Back-end Architecture, API Architecture, Design Patterns, Responsive Web Design (RWD), UI Design, UX Design, Web UX Design, Automated Testing
Storage
Relational Databases, MongoDB, MySQL, Databases, Database Modeling, PostgreSQL
Platforms
Heroku, Azure, Amazon Web Services (AWS), Dokku, Docker, Twilio, Voiceflow
Other
APIs, Full-stack, Front-end, Back-end, Web Development, API Integration, Architecture, Technical Architecture, Front-end Development, Minimum Viable Product (MVP), User Experience (UX), Software Architecture, Full-stack Development, Web App Development, MERN Stack, UI Development, Data Modeling, Software as a Service (SaaS), Single-page Applications (SPAs), Web Applications, RESTFul APIs, Back-end Development, API Design, Startups, Leadership, Mobile First, Payment APIs, Responsive Web Apps, Large Language Models (LLMs), Chatbots, Artificial Intelligence (AI), Technical Leadership, Authentication, Authorization, Solution Architecture, Integration, Browser Automation, API Testing, Algorithms, Writing & Editing, UI Animation, Web Animation, Live Chat, Cloud Storage, Charts, Styled-components, UI Components, User Interface (UI), Web Scraping, PayPal, Reports, Dashboards, Single Sign-on (SSO), eCommerce, Headless CMS, ChatGPT API, OpenAI, Vite, CI/CD Pipelines, Agentic AI
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