O Oskar Karpiński

Skills

Technologies used in real projects

My strongest areas are Kotlin, backend development and native Android applications. My full-stack experience also allows me to deliver the frontend, website, integrations and infrastructure required to launch the complete solution.

Kotlin & Backend

Kotlin jest moją główną technologią. Wykorzystuję go do tworzenia backendów, REST API, logiki biznesowej, systemów autoryzacji oraz integracji z bazami danych i zewnętrznymi usługami.

Kotlin & Spring Boot

The main backend technology used to build services, business logic and integrations in the public LibrePass project.

  • Spring Boot
  • Spring Security
  • Spring Data JPA
  • Hibernate
  • Ktor

Go

An additional backend technology for lightweight services, CLI tools, automation and concurrent tasks.

  • standard HTTP library
  • goroutines
  • context
  • SQL
  • testing
  • CLI tools

APIs and testing

Designing API contracts, authorization, documentation, and unit and integration tests.

  • Ktor
  • REST API
  • JWT
  • OpenAPI
  • JUnit
  • integration testing

Android & Mobile Development

I build native Android applications with Kotlin and Jetpack Compose. I work with modern interfaces, local data storage, synchronization, offline use, and backend communication.

Android and Kotlin

A native Android client built with Kotlin, Jetpack Compose and Material 3.

  • Android
  • Kotlin
  • Jetpack Compose
  • Material 3

Data and offline use

Local data storage, synchronization, offline operation and secure application unlock.

  • Coroutines
  • Kotlin Flow
  • Room
  • Dagger Hilt
  • biometrics
  • offline use

Web Applications & Websites

I build web applications, panels, forms and business websites connected to backend systems. I focus on responsiveness, accessibility, performance and technical SEO.

Frontend

Building interfaces, forms and dashboards connected to APIs with TypeScript and React.

  • TypeScript
  • React
  • Next.js

Websites and rendering

Creating fast websites and applications with Astro, Next.js, SSR and SSG.

  • Astro
  • Tailwind CSS
  • SSR
  • SSG
  • WordPress

Databases & Infrastructure

I design data structures and prepare the environments needed to run applications. I configure containers, a basic pipeline, and a server for the deployed solution.

Databases

Designing schemas, migrations, indexes and data structures for applications.

  • PostgreSQL
  • MySQL
  • Redis
  • schema design
  • migrations
  • indexes

Infrastructure

Containers, Linux environments and pipeline automation needed to run deployed solutions.

  • Docker
  • Docker Compose
  • Linux
  • GitHub Actions
  • CI/CD

Automation

I automate data exchange, scheduled tasks and repetitive processes by connecting services through APIs and scripts.

Automation and API integrations

Scripts and service connections supporting content publishing, data exchange and scheduled tasks.

  • API integrations
  • Python
  • web scraping
  • automation
  • scheduled tasks

Need technical support for your project?

I can help build a product from scratch, improve an existing application, or join your team.

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