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Jimmy HwangJimmy Hwang
Senior engineer · Berlin

Software that works
in the real world.

Senior product engineer: UX, product and infrastructure, built with AI. I own what goes live.

Book a call Hiring? Email me See portfolio ↓
partyx.info/console
Admin console I built: money coming in, refund requests and a dispute to answer
PartyX iOS app: tonight in Berlin
Live paymentsCheckout to refund
One engineerDesign to production
PartyX — designed, built and running in production.Explore the screens

My work runs every day at

  • Stockholm Arlanda Airport
  • ArcelorMittal
  • Eramet
  • PartyX
Services

What does your product need next?

Teams

Full time

A senior engineer in your team, owning features end to end.

From €600/day
3–12 months · start now
  • Any stack
  • Shipping in week one
  • Berlin or remote
Discuss a contract
Products

Build or rebuild

A new product, rebuild or migration, from design to launch.

By milestone
Fixed price or day rate
  • Clear milestones
  • Shipped with AI, tested
  • Launched and handed over
Discuss a build
Ongoing

Part time

A senior engineer two or three days a week.

From €600/day
Monthly · Berlin or remote
  • Fixed days each week
  • Weekly progress
  • Cancel monthly
Discuss part time

Not sure which? Book a call and we’ll pick the first step together.

Portfolio

Built, shipped, running.

Close to users.

Operators use my WiTTRA console every shift. Their feedback becomes releases.

Owns the whole system.

PartyX payments, payouts, door, deploys and cloud cost: all mine.

Ships in week one.

AI writes much of the code. I own the decisions, tests and release.

PartyX web app: events happening now in Berlin

PartyX

Designed, built and operated alone: discovery, checkout, tickets, refunds, door and the organiser console. New design shipped in 2026.

6 apps2,264 tests at releaseStripe end to end

Used every shift at Stockholm Arlanda Airport, ArcelorMittal and Eramet.

WiTTRA Networks

Customer-facing operator console, supporting APIs and realtime data. Senior engineer since 2023.

Enterprise customersContinuous releases

An ontology, a task board and a memory graph that let AI agents build PartyX safely.

How I run AI agents

Rules the agents follow, a board that orders their work, and a searchable memory of every decision. One engineer, many agents, reviewed releases.

Ontology rulesBoard for agent workGraph memory
Process

How it works.

01

15-minute call

What’s blocked and what must work. Free.

02

Written scope

Priorities, price and how we measure success.

03

Build and hand over

Tested releases. You own the code and accounts.

Jimmy Hwang

Hi, I'm Jimmy.

Senior product engineer in Berlin. I built the operator console used every shift at Stockholm Arlanda Airport, and I built and run PartyX alone.

AI does much of my typing. I focus on the users, the simplest interface, and infrastructure that stays fast and cheap.

Looking for a team in Berlin. Open to selected projects.

Before we start.

What does it cost?

Projects: fixed price after a short review. Contracts: from €600/day. Always in writing first.

How do we start?

A 15-minute call, then a written scope.

What happens after launch?

You own the code and every account. Support can be added.

Can you work on an AI-built product?

Yes. I review it first, then fix or finish what matters.

Book a call

Book 15 minutes.

Times shown in your timezone.

Prefer email? founder@partyx.infoPrefer a CV? One page, PDF