Oskar Szrajer — Software Engineer CV

Gdynia, Poland · [email protected] · +48 608 019 078 · gotar.info

linkedin.com/in/oskarszrajer · github.com/gotar

Summary

Hands-on Ruby/Rails engineer delivering web products from backend systems and APIs to user interfaces and deployment. Experienced in leading remote teams and mentoring developers. Current work includes LLM applications and AI-assisted engineering, backed by an MSc in Computational Intelligence.

Professional experience

Impactpool — Senior Software Developer

Sep 2021–Apr 2026 · Remote · Hands-on development and technical team leadership

Helped build and lead the distributed engineering team for a Rails 8 recruitment platform serving humanitarian employers, with job matching, talent pools and analytics.
Developed external API and BigQuery integrations, Hotwire interfaces (Turbo, Stimulus, ViewComponent), and Puppeteer-based scraping; used Dry-rb and Sequel for backend development.

Belighted — Senior Backend Developer

Oct 2018–Aug 2021 · Remote

Built backends for three products: financial forecasting (Hannah Online), car sharing (AXS), and GDPR documentation (Admeet), using Rails, Roda/ROM, PostgreSQL and RSpec.
Worked with GraphQL, SOAP and external APIs, using Dry-rb for business logic.

Ragnarson — Senior Ruby Developer / Co-owner

Developer: Apr 2011–Jun 2016 · Co-owner: Jul 2014–Oct 2016 · Sopot / Remote

Worked on Tripsta support systems handling 3,000+ requests/second, mobile messaging APIs and Google Ads management backends; Ruby, JRuby, Sinatra, Redis and PostgreSQL.
Established the Tricity office and helped grow the company from 10+ to 30+ developers; hired and trained developers, including 100+ interns, and supported clients as Project Manager and Account Manager.

Independent consulting & products

Gotar — Founder / Independent Software Engineer

Apr 2011–present · Gdynia / Remote

Run a Ruby/Elixir consultancy, building end-to-end web applications for international clients and providing business consulting for Rebased.
Built Rails Radar (railsradar.dev): a Rails 8 job discovery and application-tracking product with 4,500+ collected listings, CV-based matching and automated data collection. Stack: Hotwire, Solid Queue, Kamal.
Build LLM-enabled features and an engineering-workflow assistant using prompt design, structured outputs, API integration and evaluation; apply AI to research, prototyping and code review.

Core skills

Backend: Ruby · Rails · Roda · Hanami · Elixir · Sequel · ROM.rb · dry-rb · REST/GraphQL · RSpec/TDD · Sidekiq

Web & UI: JavaScript · TypeScript · React · Node.js · Hotwire · HTML/CSS · Tailwind CSS · Figma

SQL & NoSQL: PostgreSQL · MongoDB · Redis · Elasticsearch · Query optimization · Caching

Delivery & access: Linux · Docker · AWS · CI/CD · GitHub Actions · Kamal · OAuth/OIDC · Sentry

AI engineering: LLM integration · Structured outputs · Tool calling · RAG · pgvector · RubyLLM · Evaluation

Education & languages

MSc, Computational Intelligence — University of Gdańsk, 2008–2010
BSc, Computer Science — University of Gdańsk, 2005–2008

Languages: Polish · English