Bartosz Soja

Senior Software Engineer / Freelancer

Remote · Based in Poland (CET) · Working with teams worldwide

Open to contracts, freelance projects & new opportunities
LinkedIn Experience
15+ yrsbuilding software
Full-stackweb · desktop · mobile · cloud · AI

About

I'm a senior software engineer with more than 15 years of experience across frontend and backend, building web, desktop and mobile applications. I've spent most of my career on long-running, business-critical systems for international companies in healthcare information systems, life sciences, banking and defence.

My core stack is .NET / C#, Angular and Java, with mobile work on Android and iOS. More recently I've been working as a cloud / platform engineer and building AI-powered applications with LLMs, agents and evals.

Tech stack

Backend

.NETC#JavaREST APIs

Frontend

AngularTypeScriptJavaScriptHTML5CSS3

Mobile & desktop

AndroidSwift / iOSDesktop apps

Cloud & AI

Cloud / platform engineeringAWSLLMsAI agentsContext engineering

How I can help

Full-stack development

New features and products end to end: .NET or Java backends with Angular frontends.

Legacy & enterprise systems

Maintaining, modernising and extending large, regulated codebases such as healthcare software.

AI-powered apps

Adding LLM features, agents and evals to real products, built to run in production.

Experience

  1. Senior Software Engineer · SolventumCurrent

    Mar 2023 – Present

    Contract · Remote · Solventum Health Information Systems, on behalf of Mieres IT

  2. Senior Software Engineer · Self-employedCurrent

    Sep 2021 – Present

    Freelance · Android development, Swift and more

  3. Senior Software Engineer · Sartorius Stedim Biotech

    Apr 2022 – Mar 2023

    Contract · Remote · on behalf of Eleks

  4. Senior Software Engineer · 3M

    Aug 2017 – Sep 2021

    Full-time · Poznań, Hybrid · 3M Health Information Systems, on behalf of Sii Poland

  5. Senior Software Engineer · PSI Polska

    Oct 2015 – Aug 2017

    Full-time · Poznań, On-site

  6. Software Engineer · Citi

    Oct 2013 – Jun 2015

    Full-time · Poznań, On-site · Citigroup, on behalf of GFT Poland

  7. Software Engineer · Teldat

    Aug 2009 – Sep 2013

    Bydgoszcz · Battlefield Management System (BMS), a tactical C3IS command & control system · Android development

  8. Logistics Specialist / IT System Administrator · Cargo

    Nov 2007 – Aug 2009

    Bydgoszcz

Certifications

AI_devs 4: Builders

AI_devs · 5-week course on production-ready AI apps: LLM tooling, context engineering, agents, evals

Oct 2026

70-480: Programming in HTML5 with JavaScript and CSS3

Microsoft

Nov 2014

70-483: Programming in C#

Microsoft

Jan 2014

Personnel Security Clearance (NATO Secret / EU Secret)

National Security Authority

2012 – 2018

Languages

PolishNative
EnglishFull professional
GermanElementary
RussianElementary

Contact

Have a project or a role in mind?

The quickest way to reach me is a message on LinkedIn.

Message me on LinkedIn