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I build software for companies that can’t afford for it to break.

Co-founder and CTO of EXTRA, a Slovenian software studio. Twelve years on production systems across healthcare, defense, fintech and Web3 — autonomous medical robots, a regulated exchange, platforms half a million people log into.

Start a conversation Résumé (PDF)
p95 database response Hyperice
1.2s 280ms rewrite

Data layer rewritten under a fixed launch date. Held 25,000+ concurrent users at 99.8% uptime.

Case study →
12+
Years shipping production software
18
Products live in production
500k+
People on systems I built
6
Regulated domains worked in

Selected work

Four projects worth the long version

The ones that best show the depth and the stakes. Every number below is either measured or the client's own published figure.

01 Enterprise SaaS · AI 2025–present

Blissbook

Employee handbook SaaS — Notion for HR compliance, with a RAG policy chatbot, audit-grade data lineage, and enterprise auth.

Built a RAG-powered chatbot that lets employees ask plain-English questions about company policy — vector retrieval on OpenSearch, generation on AWS Bedrock, with citation markers pointing at the exact section, in-section access control so the model never surfaces what an employee shouldn't see, end-to-end message encryption, and rate-limit handling on the retrieval layer. Also led Data Lineage: every policy change tracked across versions with diffing, multi-policy reports and exportable PDFs. On top of the AI work, the un-glamorous plumbing that makes a product deployable inside a Fortune 500 — SAML/Okta SSO, real-time collaborative editing on CKEditor, PDF pipelines on Bull, S3 assets, SFTP imports, compliance-grade audit trails.

  • 500k+

    Employees served

  • RAG

    Policy chatbot

    OpenSearch + Bedrock

  • SAML

    SSO via Okta

  • Fortune 500

    Deployment tier

Read the case study →

02 Connected wellness 2019–2023

Hyperice

Backend for HyperSmart, the connected recovery platform behind Hyperice's smart devices.

Joined when the API was buckling under a growing user base. Redesigned the data layer and rewrote the critical paths in NestJS and PostgreSQL — queries that were doing per-request work that belonged in an index or a cache. Database responses fell from 1.2s to 280ms, API latency by 60%. Built integrations with Apple Health, Strava, Garmin and Whoop, each with its own auth flow, data shape and edge cases. Scaled to 25,000+ concurrent users at 99.8% uptime. Four years on the platform meant touching every layer: schema, CI/CD, on-call, incident response.

  • 280ms

    Database response time

    75% faster, down from 1.2s

  • 25,000+

    Concurrent users

  • 99.8%

    Uptime

  • 5

    Health platform integrations

Read the case study →

03 Marine engineering 2022–2025

Naval Architect

Digital-twin platform used by ship designers and marine engineers in Germany.

A three-year contract with an unusually broad stack: Angular on the front, NestJS and Django behind it, C++ for the performance-critical 3D calculations, Flutter for cross-platform tooling, all on PostgreSQL. Built modules for 3D modelling workflows, vessel data management, and synchronisation between design tools that had never been meant to talk to each other. Ship design has zero tolerance for imprecision — the workflows demand reliability over flash — so the engagement was spent raising performance and stability across the platform rather than adding surface.

  • 3 yrs

    Continuous engagement

  • 6

    Technologies in one platform

  • C++

    Performance-critical core

  • 3D

    Modelling pipeline

Read the case study →

04 Web3 platform 2024–2025

Apillon

Developer platform on Polkadot. GitHub-to-IPFS pipelines, NFT campaign tooling, RPC-as-a-Service.

Most Web3 tooling is painful to use; Apillon's whole job is to abstract that away. Built GitHub-to-IPFS deployment so a developer ships a decentralised site with a git push, the same way they'd ship to Vercel. Delivered Simplets, NFT campaign templates a non-technical user could configure and launch without writing code. Also built RPC-as-a-Service for blockchain node access, and spent the rest of the engagement pushing reliability across the storage, hosting and identity modules.

  • 1M+

    Files uploaded

  • 1,000+

    Sites deployed

  • 42,000+

    NFTs minted through Simplets

  • Git → IPFS

    Deployment pipeline

Read the case study →

Also shipped

Production systems, six industries

Defense, healthcare robotics, regulated fintech, maritime engineering. Each of these has its own case study.

Defense 2023

Rheinmetall

Product configuration manager for one of Europe's largest defense companies. Dynamic property system, audit trails, RBAC.

Angular · NestJS · Prisma · PostgreSQL

Healthcare robotics 2021

Ropca

Software for the world's first AI-powered autonomous ultrasound robot for arthritis diagnosis.

TypeScript · Node.js

Healthtech 2024–present

Bo

Mental-health platform with guided exercises and live video therapy. Cross-platform monorepo with shared types.

React Native · NestJS · Prisma · Stripe

Regulated fintech 2023

Floin

Regulated VASP crypto trading platform in Liechtenstein. Buy, sell, tokenise — with full FMA compliance.

TypeScript · Node.js · React Native

Fintech 2023–2024

Mountain Green

Direct-sales platform for a hemp-products company. Multi-tier commission engine, real-time distributor dashboards.

React · AWS Lambda · AWS Amplify · MySQL

Wealthtech 2025–present

Jonatan Mars

Investment-management app with KYC, document signing and portfolio tracking. iOS, Android and web from one Expo codebase.

React Native · Expo · Supabase · SumSub

Travel marketplace 2023–2025

Megabon

Travel-deals marketplace front-end. Performance- and SEO-optimised Next.js on a shared-package monorepo.

Next.js · Node.js · Heroku

Maritime 2022–2025

SeaVizor

Shipbuilding project management. Real-time jobsite tracking, a mobile app for technicians, a web control centre for coordinators.

Angular · Django · PostgreSQL · Flutter

Your project

Something in this shape?

Most of these started as one conversation about a system that had to work.

Get in touch →

What I get hired for

Three things, done properly

01

Backend systems that hold under load

APIs, data layers and infrastructure for products where downtime is a business event. Query profiling, schema and index design, caching, load testing against honest traffic models, monitoring and the runbook that goes with it. The Hyperice backend went from 1.2s database responses to 280ms and held 25,000+ concurrent users through a launch window.

  • NestJS
  • PostgreSQL
  • Redis
  • AWS
  • Terraform

02

AI features that survive an audit

Retrieval-augmented generation wired into products that have compliance officers. Vector retrieval, citation markers so an answer points at its source, per-section access control so the model cannot surface what a user is not cleared for, message encryption, and rate-limit handling on the retrieval layer. The interesting part of AI work is everything around the model.

  • AWS Bedrock
  • OpenSearch
  • RAG
  • TypeScript

03

Products shipped end to end

Whole products, from the schema to the app store listing: web front-ends, cross-platform mobile, payments, KYC, document signing, CI/CD. Usually as the person a founder or a CTO hands the hard half to. Twelve years of this across eighteen products means most of the expensive mistakes have already been made once, somewhere else.

  • React
  • React Native
  • Expo
  • Next.js
  • Astro

What’s next

Got something that can’t break?

Fractional CTO work, a backend that needs rescuing, an AI feature that has to survive a compliance review — or just a second opinion on an architecture. Tell me what you’re building and I’ll tell you straight whether I’m the right person for it.

Email me LinkedIn

or write to purg.jaka@gmail.com