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Andrei Koleda
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Portrait of Andrei Koleda

I'm, Andrei Koleda

koleda05@gmail.com

Full-stackweb developer

6 years building production web applications with TypeScript, React, Next.js and Node.js. I work across the whole stack, from UI and APIs to databases, third-party integrations and cloud infrastructure, and I build AI into products with LLM APIs, MCP and RAG, using AI-assisted development in my daily work.

See selected projectsDownload CV (PDF)

6

years of commercial experience

C1

English & Polish

Graduate

Mathematics & Informatics, Łódź

Now

AI integrations, LLM APIs & MCP

01 / Selected work

Projects

Commercial products I've worked on, with what I built on each. Live links where the product is public.

Patriot Mail

An email client that connects to the mailbox you already have. Users keep their current address and provider, and only the experience changes.

What I built

  • Developed a multi-provider email client on a custom IMAP/SMTP proxy architecture designed to keep user email data private.
  • Integrated OAuth 2.0 sign-in for Google, Microsoft, Yahoo and Apple.
  • Implemented accessibility features for elderly and disabled users.
  • Integrated PostHog for error tracking and conversion analytics.
  • Next.js
  • Node.js
  • Cloudflare Workers
  • IMAP/SMTP
  • OAuth 2.0
  • AI integration
  • Playwright
  • CI/CD
  • Docker
Visit patriotmail.ai (opens in a new tab)
Case study: problem, role and technical notes

The problem

People with long-held addresses at Gmail, Outlook, Yahoo or iCloud often want a calmer, more readable inbox without migrating to a new provider. The client has to work on top of those existing accounts rather than replace them.

My role

Full-stack developer at Sanddev, working on the client, its backend and the provider integrations.

Technical notes

Multi-provider mail access
Mail is read and sent over IMAP/SMTP through a custom proxy layer (imapflow), so one client can talk to many providers while user email data stays private.
Authentication
OAuth 2.0 flows for Google, Microsoft, Yahoo and Apple, so users connect accounts through each provider's own sign-in.
Accessibility
Implemented accessibility features aimed at elderly users and users with disabilities.
Observability
Integrated PostHog for both error tracking and user conversion analytics.

Full stack

TypeScript · Next.js · Node.js · Cloudflare Workers · IMAP/SMTP (imapflow) · SQLite · OAuth 2.0 · PostHog · AI integration · Playwright · CI/CD · Docker

Patriot Mail landing page with the headline “Keep your email address. Upgrade everything else.”
Public landing page, patriotmail.ai

Enterprise Affiliate & Attribution Engine

An ad network platform that tracks advertising campaigns and records the results on the BSV blockchain.

What I built

  • Developed synchronisation with Cloudflare R2 storage.
  • Integrated SendGrid for email delivery.
  • Integrated the Everflow API for campaign tracking.
  • Built a custom email template editor with cloud-based asset management.
  • Next.js
  • Node.js
  • PostgreSQL
  • Redis
  • Cloudflare R2
  • Playwright
  • CI/CD
  • Docker
Internal platform, no public link
Case study: problem, role and technical notes

The problem

Affiliate campaigns produce tracking data across several external systems. The platform has to bring that data together, deliver campaign email, and record results on the BSV blockchain.

My role

Full-stack developer at Sanddev, focused on integrations, storage and the email tooling.

Technical notes

Campaign tracking
Integrated the Everflow API as the source of campaign tracking data.
Storage sync
Built synchronisation with Cloudflare R2 storage.
Email tooling
Integrated SendGrid for delivery and built a custom email template editor with cloud-based asset management.
Codebase
A Turborepo monorepo on Next.js and Node.js with PostgreSQL, Redis and Playwright end-to-end tests.

Full stack

Next.js · TypeScript · Node.js · Cloudflare Workers · PostgreSQL · Redis · Turborepo · Playwright · BSV blockchain · CI/CD · Docker

Enterprise Affiliate & Attribution Engine

  • Everflow API
  • Cloudflare Workers
  • PostgreSQL
  • Redis
  • Cloudflare R2
  • SendGrid
  • BSV blockchain
Illustration of the services involved, not a screenshot

Sandtime.io

A web platform for time tracking, timesheets, reporting and managing employees' work.

What I built

  • Built an AI chatbot based on intent classification, RAG and MCP, so users can operate the application by chatting instead of navigating the interface manually.
  • Improved application performance, including updates to caching.
  • Built time tracking reports for users.
  • React
  • Express.js
  • MongoDB
  • TypeScript
  • AI integration
  • Playwright
  • CI/CD
  • Docker
Visit sandtime.io (opens in a new tab)
Case study: problem, role and technical notes

The problem

Teams use Sandtime.io every day to log time, fill in timesheets and report on work. The app has to stay fast, and common actions should be quick to reach without clicking through many screens.

My role

Full-stack developer at Sanddev, working on the AI chatbot, performance and reporting.

Technical notes

AI chatbot
Intent classification works out what the user wants, RAG grounds the answers, and MCP lets the assistant carry out actions in the application.
Performance
Performance improvements across the app, including updates to caching.
Reports
Time tracking reports that give users an overview of their logged time.
Testing and delivery
Playwright end-to-end tests and a CI/CD pipeline with Docker.

Full stack

React · TypeScript · Express.js · MongoDB · AI integration · RAG · MCP · Playwright · CI/CD · Docker

Sandtime.io landing page showing the time tracking dashboard
Public landing page, sandtime.io

Suppression List Management

An application that helps ad networks and marketers manage suppression lists, so people who opted out are not contacted again.

What I built

  • Integrated SendGrid for sending suppression list data.
  • Implemented historical data tracking and real-time activity monitoring using Cloudflare services.
  • Created a reporting and analytics system.
  • Next.js
  • Node.js
  • PostgreSQL
  • Cloudflare
  • SendGrid
  • Playwright
  • CI/CD
  • Docker
Internal product, no public link
Case study: problem, role and technical notes

The problem

Ad networks and marketers must not contact people who have opted out. Suppression lists have to stay current and reach the systems that send the messages.

My role

Full-stack developer at Sanddev, working on the SendGrid integration, activity monitoring and reporting.

Technical notes

Delivery of list data
Integrated SendGrid for sending suppression list data.
History and monitoring
Historical data tracking and real-time activity monitoring built on Cloudflare services.
Reporting
A reporting and analytics system on top of the collected data.
Testing and delivery
Playwright end-to-end tests and a CI/CD pipeline with Docker.

Full stack

Next.js · TypeScript · Node.js · PostgreSQL · Cloudflare · SendGrid · Playwright · CI/CD · Docker

Suppression List Management

  • SendGrid
  • Cloudflare
  • PostgreSQL
  • Next.js
Illustration of the services involved, not a screenshot

Choice

Website for Choice, an Apple device repair service in Warsaw, with device-specific service pages, a price list and visit booking.

What I built

  • Built the whole website from scratch: the UI, the application logic and the structure of devices and repair services.
  • Integrated third-party platforms, including Stripe and Klarna payments.
  • Set up SEO and tuned performance.
  • Next.js
  • NestJS
  • PostgreSQL
  • Cloudflare
  • Stripe
  • SEO
  • Playwright
  • CI/CD
  • Docker
Visit thechoice.pl (opens in a new tab)
Case study: problem, role and technical notes

The problem

A repair service covers many Apple devices and many kinds of repair. Customers need to find their device and service quickly, see prices, book a visit and pay online, and the site has to be found in search.

My role

Sole developer: built the site from scratch, from the interface to the backend and integrations.

Technical notes

Devices and services
Designed the logic and structure of devices and repair services that the service pages and price list are built from.
Payments
Integrated Stripe and Klarna.
SEO and performance
Set up SEO and tuned the site's performance.
Testing and delivery
Playwright end-to-end tests and a CI/CD pipeline with Docker.

Full stack

Next.js · NestJS · PostgreSQL · Cloudflare · Stripe · Klarna · SEO · Playwright · CI/CD · Docker

Choice homepage with the headline “Serwis Apple klasy premium w Warszawie”
Public website, thechoice.pl

02 / Career

Experience

  1. –

    Sanddev Sp. z o.o.

    Full-stack Web Developer

    Frontend and backend work on web applications for advertising, marketing and email products, using TypeScript, Next.js and Node.js with PostgreSQL and Cloudflare. Day to day this covers third-party integrations, authentication, email infrastructure, analytics and data processing. More recently it has also meant AI integrations, LLM APIs and AI-assisted development.

    Products

    • Patriot MailMulti-provider email client
    • Affiliate & Attribution EngineAd network tracking platform
    • Suppression List ManagementCompliance tooling for marketers
    • Sandtime.ioTime tracking and project management

  2. –

    IntexSoft

    Full-stack Web Developer

    Web applications for education, banking and industrial automation. Mostly frontend work in React, Redux and TypeScript, plus backend services, PostgreSQL and API integrations. Backend stacks varied by project.

    Also worked with: GraphQL · Java · C#

    Products

    • BlackboardVirtual learning environment and LMS
    • Banking client managementWeb app for managing bank clients
    • HMI Web EngineFramework for configuring distributed automation and simulation systems in steel production

03 / Toolbox

Skills

04 / Background

About

I've spent six years building web applications for advertising, marketing, education and banking. Most of it in TypeScript, React, Next.js and Node.js, and much of it on the parts behind the interface: backend services, databases, third-party APIs and cloud infrastructure.

Lately that has meant email infrastructure, OAuth across several providers, ad-tech integrations and Cloudflare Workers. I've also been working more with LLM APIs and AI-assisted development.

I've lived in Poland for the past ten years and studied mathematics and informatics in Łódź. Programming started as a long-term interest and became my profession.

Location
Poland
Education
Lodz National University, Faculty of Mathematics and Informatics (2017 – 2020)
Languages
Polish C1, English C1
Looking for
A team where I can use my experience, take on new challenges and keep growing as an engineer

05 / Contact

Hiring for a full‑stack or frontend role?

I'm looking for a team where my experience across the stack is useful from the start. Email is the quickest way to reach me, and I'm happy to walk through any of these projects in more detail.

koleda05@gmail.comDownload CV (PDF)
Andrei Koleda smiling and pointing at the viewer