Available for new opportunities
Hi, I'm Bartłomiej
Software
Developer
@ bkosinski.dev
4+ Years of Experience
01
/
About Me
I’m on a journey to reach the highest level possible, building things that are fast, secure, and enjoyable to work with.
That mindset naturally leads me to creating tools that help developers move faster and work more efficiently — from reusable components to cleaner, more .
Curiosity drives me to explore new and understand them on a deeper level.
To me, good engineering isn’t about chasing the newest tools, but about choosing the right tools for the right problems — and understanding them deeply enough to use them with confidence.
When I’m not coding, you’ll probably find me reading , experimenting in the , or exercising.
TypeScript
Type-safe approach
Seamlessly bringing API types into the web environment with OpenAPI, monorepos, and automated code generation, regardless of the programming language or framework.
Performance
Optimizing build and test times by picking right tools, caching and making sure code-splitting is effective. Continuously tracking and eliminating latency and performance bottlenecks in applications.
Testing & Quality
Ensuring high code quality through unit, integration, and end-to-end testing. Catching issues early and maintaining confidence when refactoring or shipping new features.
Security
Applying modern security standards and best practices, including secure authentication flows, proper data validation, monitoring including OpenTelemetry and safe API communication.
02
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TechStack
The tools and technologies I use to design, deploy, and operate infrastructure at work.
Frontend
Vite Vite
React React
TanStack Start
Next.js Next.js
Redux Redux Toolkit
Turborepo Turborepo
Nx Nx
Zustand
UI / Styling
Sass Saas
Tailwind CSS TailwindCSS
Framer Motion
Form / Validation
TanStack Form
React Hook Form React Hook Form
Formik Formik
Zod Zod
ArkType
Yup
Backend
Node.js Node.js
Express Express
NestJS NestJS
Fastify Fastify
Node-RED Node-RED
Laravel Laravel
Testing / Documentation
Jest Jest
Vitest Vitest
Testing Library React Testing Library
Playwright
PHPUnit
Nextra Nextra
Storybook Storybook
Databases / ORM
MySQL MySQL
PostgreSQL PostgreSQL
MongoDB MongoDB
Redis Redis
Drizzle Drizzle
Prisma Prisma
Laravel Eloquent
Containers & CI/CD
Docker Docker
GitHub Actions Github Actions
03
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Carrier Journey
  1. Full-Stack Developer, Frontend Lead

    - Designed and implemented modular architectures for on-premise ERP and MES systems
    - Developed and maintained backend services in PHP and Node.js (databases, data integrity, event-driven architecture)
    - Maintained and evolved existing systems to meet business and reliability requirements
    - Integrated external systems and devices, collaborated directly with clients
    - Created and maintained internal technical documentation
    Docker
    Laravel
    MySQL
    NestJS
    Node.js
    PHPUnit
    React
    Redis
    Slim
    TypeScript
    Vitest
  2. Technical College for Computer Science

    - Laureate of Polish Technical Innovation and Invention Olympiad in category didactic help (co-creator of educational web platform Live-Text for online learning and examing).
    C++
    JavaScript
    MySQL
    PHP
    WebSockets
04
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Projects
process-diagram
Shipment Tracking
Vague shipment statuses from the official app are resolved by automating tracking via Poland Post's public SOAP API, with email notifications for each update.
process-diagram
app
NestJS
React
SOAP
TanStack Start
TypeScript
process-diagram
Book Collections
To address duplicate book orders and incomplete entries on platforms like Goodreads, a personal library management system tracks the entire collection, including multilingual titles, and efficiently manages reading history.
process-diagram
app
app
ArkType
ClickHouse
Docker
Fastify
GraphQL
Kafka
Mercurius
NestJS
PostgreSQL
React
Redis
TanStack Start
TypeScript
process-diagram
Portfolio
Motion
Next.js
React
TailwindCSS
A personal portfolio built with Next.js and React to showcase projects and experience. It features smooth animations with Motion and a clean, responsive design.
WebSocketKit
Issues with missing type definitions and unstable real-time listeners in the provided SDK are resolved by introducing a type-safe abstraction that centrally manages listener lifecycles, ensuring unsubscribe is triggered only when no active listeners remain.
Pusher
TypeScript
Vitest