Oskar Szrajer

Impactpool — Senior Software Developer

Sep 2021–Apr 2026 · Remote

Scope: hands-on backend development and technical team leadership.

• Helped build and lead the distributed engineering team for a Rails 8 platform connecting humanitarian employers with qualified talent.
• Worked on job matching, talent pools and analytics, including BigQuery and external API integrations.
• Developed dynamic interfaces with Hotwire (Turbo and Stimulus) and reusable ViewComponent UI elements.
• Integrated Puppeteer-based web scraping, Dry-rb business logic and Sequel database access.

Belighted — Senior Backend Developer

Oct 2018–Aug 2021 · Remote

• Built the backend for Hannah Online, a financial forecasting application, using Rails, PostgreSQL, GraphQL, Dry-rb and RSpec.
• Developed the backend for AXS, a car-sharing platform with external API and SOAP integrations.
• Built backend functionality for Admeet, a GDPR documentation generator, using Roda, ROM, PostgreSQL and GraphQL.

Ragnarson — Senior Ruby Developer / Co-owner

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

• Worked on Tripsta (TravelPlanet) high-performance support systems handling 3,000+ requests/second, using Ruby, Goliath, Sinatra and Redis.
• Built backend systems for Getmii (geo-based messaging APIs for iOS and Android), MaMyMo (Google Ads management), Locafox (location-based price comparison) and Masii (financial product comparison).
• Used Ruby, JRuby, Roda, ROM, Dry-rb, PostgreSQL, Elasticsearch and RSpec; also worked on Rails/Spree e-commerce and ActiveAdmin applications.
• Established the Tricity office and helped grow the company from 10+ to 30+ developers.
• Hired and trained developers, including 100+ interns, and worked directly with clients as Project Manager and Account Manager.

Gotar — Founder / Independent Software Engineer

Apr 2011–present · Gdynia, Poland / Remote

• Run an independent Ruby/Elixir consultancy, building end-to-end web applications and systems for international clients.
• Provide business consulting for Rebased Software House, drawing on experience in engineering, team development and client-facing work.

Readarr — Deployed personal AI application

Rails 8 · Hotwire · LLM translation · Output evaluation · Solid Queue

• Built and operate a novel reader with 1,900+ LLM-translated and automatically reviewed chapters, using glossary and continuity context for English-to-Polish translation.
• Implemented source-aware LLM review with structured verdicts, scores and corrections, plus deterministic checks for missing segments, truncation, duplicate text and malformed output; reject invalid candidates before publication.
• Compared translation models on a shared chapter using output-quality review, latency and cost considerations; added regression tests for failures observed in deployed use.

Rails Radar — Live independent product

Rails 8 · Hotwire · Self-hosted AI extraction · Solid Queue · Kamal

• Built a job discovery and application-tracking product with 5,100+ collected listings, CV-based role matching, geography checks and private application tracking.
• Integrated self-hosted AI extraction with 2,400+ listing extraction records; promote facts only above configured confidence thresholds and retain model answers and overwritten values for auditability.
• Keep collection independent of AI availability, with bounded background processing, retries and manual profile values remaining authoritative.

Personal AI Assistant & Multi-Agent Workflow Assistant

Rails 8 · Pi agent integration · Retrieval · Slack / Telegram · Multi-agent orchestration

• Built a personal AI assistant: a Rails interface around the Pi agent runtime, with streaming responses, tool execution tracking, project-specific working directories and QMD-backed knowledge retrieval.
• Integrated Slack and Telegram gateways, scheduled automation and runtime monitoring, including retry and dead-letter handling for outbound messages.
• Built a Slack-native multi-agent workflow assistant (MVP) with manifest-based agent selection, per-agent working directories, validated JSON result contracts and persisted run/task/event history.