Piotr Usewicz
Senior Software Engineer
Benicàrlo, Spain · Remote (CET, EU/US overlap)
[email protected] layer22.comgithub.com/pusewiczlinkedin.com/in/piotrusewicz Download PDF ↓
Software engineer with 20+ years of building web products, most of them in Ruby on Rails. I spent eleven years at Harvest shipping across the whole stack — platform rebuilds, public APIs, integrations, zero-downtime data migrations, developer tooling. Comfortable owning a product from database schema to deploy pipeline; happiest on a small team that ships.
Experience
Sabbatical — systems programming, games & open source
A deliberate year off after eleven years at Harvest, spent learning in public.
- Contributed 19 merged pull requests upstream to Cute Framework, a C game framework.
- Built bielik2d, a 2D game engine in pure Swift 6 on SDL3's GPU API, running natively and in the browser (WebAssembly/WebGPU).
- Shipped cf-mcp, an MCP server that gives LLM coding agents searchable Cute Framework documentation (4,500+ downloads).
- Wrote three games in C with SDL3 and Cute Framework while learning the language; made agentic coding workflows part of daily practice.
Senior Software Engineer · Harvest
Remote
Time tracking and resource planning SaaS used by 70,000+ companies; fully remote team across nine time zones. Promoted from Software Engineer in July 2021.
- Rebuilt Harvest's embeddable button and widget platform as a React + TypeScript app and shipped it to all customers, coordinating directly with Asana's engineers to keep their desktop integration unbroken.
- Drove the datastore evaluation for the new Events API — built a complete Firestore prototype in under a week and led load tests across MySQL, Firestore, and Elasticsearch; the data reversed the planned choice before it got expensive.
- As Engineering Lead of the Integrations squad, shaped the 2024 roadmap with Product and shipped the Deel payroll integration, designing a timesheet sync that worked around third-party API rate limits.
- Consolidated the Linear, Notion, Monday.com, and Trello browser extensions into one Vite codebase building for Chrome, Edge, and Firefox.
- Self-assigned and completed a multi-year migration to ISO currency codes across the Rails monolith — coordinated database migrations with SRE, zero service disruption.
- Co-built Harvest Developer Tools, cutting new-engineer environment setup to under 30 minutes.
- Modernized the frontend from Backbone/jQuery to React and Preact; shipped Google Calendar and Outlook integrations, MFA, and critical security fixes.
- Mentored six engineers, designed the team's technical interview exercises, reviewed up to 193 PRs per half-year, and helped set Harvest's direction for AI features in 2025.
“Piotr is a deeply experienced engineer with a pragmatic approach and an exceptional ability to cut through complexity. … Any team would benefit from Piotr's technical expertise, critical thinking, and collaborative spirit.”
Senior Software Engineer · Homestay.com
Dublin, Ireland
- Designed and implemented core services of the vacation-rental platform (Rails, MySQL) as the product scaled through public launch.
Senior Software Engineer · Mixbook
Palo Alto, California
- Shipped customer-facing Rails features on the photo products platform.
Senior Ruby on Rails Developer · HouseTrip
London, UK
- Helped build out the development team and engineering processes at a fast-growing holiday-rental startup.
“A great Ruby/Rails developer, Piotr is a good communicator, easy to work with and delivered high quality code in a challenging, high traffic app.”
Application Developer · AOL
London, UK
- Built scalable realtime applications in Node.js and Erlang.
“I've worked with Piotr twice and he was so good the first time I made sure AOL got him when he was available again. … Hire him now, before someone else does :)”
Application Developer · Mobile Interactive Group
London, UK
- Kickstarted and led the ground-up rewrite of MIGPay, the group's mobile payments platform (Ruby on Rails + Merb) — new integration tooling for partners and a new mobile web experience for end users.
- Built distributed Erlang systems and SMS payment flows powering digital-goods sales.
“Piotr has shown extraordinary dedication and expertise in recent work for Mobile Interactive Group. His passion for innovation has allowed MIG to participate in cutting edge development.”
Earlier roles
Warsaw, Poland
- Head developer at ITSS (PHP content management and e-commerce); led the design and build of an ITIL-based ServiceDesk platform in Ruby on Rails at Exorigo.
Open Source
Writing open source since 2008 — gems downloaded ~97,000 times. Everything at github.com/pusewicz.
- statique — static site generator in Ruby, built on Roda
- cf-mcp — MCP server giving LLM agents searchable Cute Framework docs
- vimpk — Vim package manager in Ruby
- bielik2d — 2D game engine in Swift 6 on SDL3, native + WebAssembly
Skills
- Primary
- Ruby, Rails, MySQL/SQL, GraphQL, REST API design
- Frontend
- JavaScript, TypeScript, React, Preact, Hotwire/Stimulus, Tailwind
- Also
- C, Swift, mruby; production Erlang, Node.js and PHP in past lives
- Practices
- TDD, code review, zero-downtime migrations, load testing, developer tooling, AI-assisted development
- Languages
- Polish (native) · English (fluent) · Spanish (intermediate)