Trefon.
whoami AI Systems Engineer

I write the code.

I’m Jacek Trefon. I’ve been writing software for 28 years. These days I build models, modify inference engines and write agent harnesses, mostly in C++, Rust, Swift and Python, and in whatever stack the client runs.

I work alone, on purpose. You talk to the person who writes the code, and the person who writes the code is accountable for it working.

Based in Marbella, Spain. Working globally in English, Spanish and Polish.

years writing software
28
years writing software
engineers led at CAFU
100+
engineers led at CAFU
regions, one platform at Logiswift
4
regions, one platform at Logiswift
Jacek Trefon
fig. 01 — Jacek Trefon, Marbella 36.51°N 4.88°W
§01 github.com/jtrefon

Open source

§02 career

Before this

Years of leading engineering are why my builds survive production.

  1. Head of Engineering, Logiswift

    Logistics platform handling millions of transactions, microservices across 4 global regions.

  2. Head of Engineering, CAFU

    Led engineering through hypergrowth, 100+ engineers.

  3. Head of Technology, DEX Crypto

    Trading platform, matching engine and compliance infrastructure for a licensed exchange.

  4. CTO / Technology Director, Azolver

    Global logistics analytics platform, rebuilt after the Pitney Bowes divestiture.

§03 refs

From people I’ve built with

Jacek's technical knowledge far surpassed that of others and he was of tremendous benefit to the project. Brought very useful real-world development perspectives.
Sean C. Development Manager, Citco Fund Services
Highly capable and efficient, understands the development landscape intimately. A great addition to any large or small scale development team.
Keith L. MD and Founder, Strategem iLabs
Laser sharp, goal oriented, and super helpful at the same time.
Bartek C. CTO, Automotive & Mobility

Got a problem the API couldn’t solve?

Describe your problem

30-minute technical call with the engineer who builds it. No sales team, no slides.