Marcin Jarota

Senior full-stack and AI product engineer

Complex systems. Useful products.

I build AI-powered products, with coding agents in my workflow and hands-on engineering from schema to screen.

Selected workLet’s talk

Open to opportunities

Companies I’ve worked with.

What I worked on
  • Software Engineer
  • Frontend / Full-stack Engineer
  • Frontend Engineer
  • Network Operating Center

Working Mode

Whole-product engineering, from schema to final page load.

Working mode

I like the whole arc of a product — from schema and architecture to the last 50ms of page load. Lately I am deep in AI-powered systems: agents, document pipelines, and tools that make other engineers faster.

I work best where product judgment and engineering depth meet: ambiguous systems, messy workflows, and teams that need reliable delivery without hiding complexity under the rug.

Selected professional work

@ Flyps · client project

AI-enabled applications

An analytics product with LLM features.

My role

Solution design, frontend and backend. Took part in production deployments and added monitoring dashboards and alerts.

  • Wrote the design doc for moving a product feature to async background processing, then built it after team review.
  • Built the LLM processing pipeline and the integration with the product's AI assistant.
  • Ran model evaluations on output quality, cost and latency to back the model choice.
  • Created an AI-agent workflow that automates the release process, with gates and human-in-the-loop approval.
  • Solution design
  • Async processing
  • LLM integration
  • Model evaluation
  • Observability
  • Release automation

@ Flyps · client project

Data-intensive web applications

A document and workflow platform with interactive maps.

My role

Frontend and backend, as part of the team.

  • Co-built the in-app AI assistant: a real-time chat that can trigger actions in the app.
  • Co-built the document template and workflow form features.
  • Co-built the interactive map module for geographic data.
  • Worked on authentication, including SSO login, and on cloud infrastructure.
  • Real-time features
  • LLM integration
  • Authentication
  • Document templates
  • Interactive maps
  • Workflow forms

Peer Feedback

What collaborators say.

Originally published as LinkedIn recommendations.

Marcin is the person you want in your corner when things get complicated. Broad full stack expertise, sharp technical instincts, and the kind of calm confidence that makes him a natural tech lead.

Working with him feels like anything is on the table. One of those rare engineers where the answer is rarely "no" and more often "give me a moment."

Patryk Radtke

Product Designer | AI Design Engineer

Patryk worked with Marcin on the same team

In the very first week of our cooperation Marcin surprised me with how fast he got familiar with the project and started delivering value for the client. Our platform is huge, maintained by dozens of developers, the codebase changes very dynamically, yet Marcin was not afraid to jump onto that crazy train and proved to be a trustworthy team member, dedicated to fully understand the matter he's dealing with, or the root of an issue he is fixing. …

Krzysztof Borkowski

Technical Team Lead at Divante

Krzysztof managed Marcin directly

Marcin is one of those developers who demands a lot from himself. He constantly looks for improvements in his work, proactively proposes new solutions, and analyzes the solutions of other developers with great perspicacity, bringing tremendous value to the entire team. Additionally, he maintains the perfect balance of self-confidence and humility, which makes it clear to everyone that he is an excellent team player whose overriding goal is to deliver a polished product. …

Wojciech Golonka

Software Engineer at Flyps

Wojciech worked with Marcin on the same team

Public GitHub work

Selected repositories across product architecture, tooling, and open source.

Public repositories with direct links to the code.

Public repo · AI agent

Taskly: unit test keeper

GitHub ↗

A Claude Code agent that keeps unit tests up to date on every pull request.

  • A custom agent and two reusable skills (decide what needs tests, write tests), wired into GitHub Actions.
  • CI does not trust the agent: it re-runs tests and typecheck, reverts changes outside test paths, and posts a sticky PR report.
  • Mutation checks find weak tests; coverage thresholds set after a full pass (backend ~99% lines, frontend ~91%).
  • Secrets stripped from test processes, push token scoped to the push step, forks never reach the agent job.
  • Label-triggered runs, $0 for docs-only PRs, and a per-run budget cap.
  • Claude Code
  • GitHub Actions
  • TypeScript
  • Vitest
  • CI/CD
Public repo · AI product

Job Flow

GitHub ↗

A job search tracker with AI analysis of a CV against a job description.

  • Astro 5, React 19 and Tailwind 4 on Supabase (auth + Postgres with RLS), with LLM calls through OpenRouter.
  • Unit tests (Vitest, Testing Library, MSW) and E2E tests (Playwright) running in GitHub Actions.
  • Spec-first: PRD, API, DB, auth and testing plans written before the code.
  • Astro
  • React
  • Supabase
  • LLM
  • Playwright
Open source · contributor

Coinpaprika packages

GitHub · Node.js client ↗GitHub · Currency widget ↗

The official Node.js API client and an embeddable cryptocurrency market widget.

  • Contributed releases, tests, endpoint updates, dependencies, and package tooling.
  • JavaScript
  • Node.js
  • API client
  • SCSS
  • npm

AI-native workflow

Tools, not boundaries.

I work with coding agents and choose technologies to fit the problem. Architecture, verification, and the finished product are still my responsibility.

2,634 contributions in the last year

OctNovDecJanFebMarAprMayJunJulAugSepOctMonWedFri

AI tools

  • Claude Code
  • pi

Frontend

  • Next.js
  • React
  • Vue 3
  • TypeScript

Backend

  • Go
  • Node.js
  • Bun
  • Deno
  • Express
  • Hono

Data

  • PostgreSQL
  • Redis
  • SQLite

Infra

  • Docker
  • GCP
  • CI/CD

Practices

  • DDD
  • Clean Architecture
  • Testing
  • Performance

Experience

Where I’ve shipped before.

Condensed work history, focused on proof bullets rather than job-description filler.

2022–present

Software Engineer

Full-stack engineering for client products, including AI-enabled applications and data-intensive workflows.

2019 – Feb 2021

Frontend / Full-stack Engineer

Split a monolithic webpack bundle and sped up key pages on a high-traffic crypto site; shipped Vue features.

Feb 2021 – May 2022

Frontend Engineer

Built Vue components with Adobe Experience Manager and CI/CD workflows.

2017–2019

Network Operating Center

Worked on security monitoring and operational visibility on the ELK stack.