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Freelance Back-end Developer & Penetration Tester

Jaycee曾令强.

Portfolio / Developer

Building secure, resilient back-ends — and breaking them first. Still believing a little magic belongs in every line of code.

Role
Freelance
Focus
Back-end / Security
Exploring
AI & ML
BACK-END ARCHITECTURE•PENETRATION TESTING•AI & MACHINE LEARNING•BACK-END ARCHITECTURE•PENETRATION TESTING•AI & MACHINE LEARNING•

( What I do )

Build it. Break it.
Make it better.

Hover or tap a discipline to explore

  • APIs, services and data layers designed to stay fast, observable and easy to change, with security considered from the first diagram.

    • Python
    • Java
    • PHP
    • TypeScript
    • GraphQL
Jaycee's desk at night: a plush toy resting on a backlit laptop keyboard beside a wireless mouse

01 / 04

Back-end Architecture

( Experience )

Where I've worked

06 roles · newest first

  1. 01

    Smart Contract Back-End Engineer

    Phantom

    Jun 2026 — Present

    Present

  2. 02

    Penetration Tester

    MoonPay

    Dec 2025 — Present

    Surabaya, East Java, Indonesia · Remote

    Present

  3. 03

    Vulnerability Assessor

    Web3 Foundation · Contract

    Mar 2023 — Present

    Surabaya, East Java, Indonesia · Remote

    Present

  4. 04

    Smart Contract Backend Engineer

    Serotonin · Contract

    Aug 2025 — Jan 2026

    Completed

  5. 05

    Back-End Golang Engineer

    WalletConnect · Freelance

    Mar 2024 — Mar 2025

    Completed

  6. 06

    Front-End Developer

    Zurich Insurance · Freelance

    Sep 2022 — May 2023

    Completed

( About me )

A little story

Born
Surabaya
27th February 2008
Hobby
K-drama & C-drama
Watching Korean & Chinese dramas
Sport
Badminton & Padel
Racket sports

Chapter 01 — Once upon a time

Once upon a time (well, currently), a Computer Science student set off on a quest to make sense of Artificial Intelligence and Machine Learning. But deep down, I never really stopped being a Disney kid, the kind who grew up truly believing magic was real, and that belief never quite faded. I'm utterly enchanted by the beauty of far-off lands, especially Europe, Australia, and North America, exploring their wonder mostly through blogs, vlogs, and movies. And somehow, that same 'anything's possible' spirit always finds its way into every project I build, because it turns out even code needs a little pixie dust and imagination to truly come to life.

Chapter 02 — The quieter chapters

There are quieter chapters behind that love of magic. I live with major depressive disorder, and there have been times when sleep was difficult, my body felt exhausted, and the things I usually enjoyed seemed far away. I could still look like myself to other people while struggling to answer a message or follow through on a plan. Sometimes, I buried myself in work because staying busy felt easier than explaining why I was pulling away from people I cared about. I had returned to a psychiatrist for help, but finding the words to tell my friends was its own difficult step.

Chapter 03 — Room to speak

In one of those chapters, one of my close friend gave me room to speak. What began as an ordinary late-night conversation became a chance to share things I had been keeping to myself. She listened, asked questions, and offered a choice I appreciated: whether I wanted her to respond or simply hear me out. I could talk without having to turn everything into a clear explanation. And in the days that followed, she kept including me in the ordinary plans I was so often tempted to avoid.

Chapter 04 — The message I never sent

One of those moments stayed with me. I was about to cancel an outing and had started writing the message. When I opened our conversation, I remembered her encouragement. I was still overthinking; leaving the house still felt difficult. For a while, I went back and forth in my head. Then I deleted the draft and went. Later, I thanked her, a little awkwardly, because something she had said in a conversation had helped me make a decision that felt much harder than it probably looked.

Chapter 05 — Still here

There is more to living with depression than I can fit into a few paragraphs, and that evening did not resolve everything I was facing. But I want this part of my story to have a place here, too: a friend who made room for what I was carrying, a message I never sent, and an evening I almost missed. Alongside my love of imagined worlds, I am grateful for moments like that in this one.

A few things that keep me curious

  • 01Artificial intelligence & machine learning
  • 02Stories that spark imagination
  • 03The beauty of far-off places

( Education )

The long way here

  1. 2026 — Present

    Integrated Institute of Science and Technology Surabaya (ISTTS)

    UniversitySurabayaCurrently studying

  2. 2023 — 2026

    Saint Paul Catholic Senior High School

    Senior High SchoolJember

  3. 2020 — 2023

    Maria Fatima Catholic Junior High School

    Junior High SchoolJember

  4. 2017 — 2020

    Maria Fatima Catholic Elementary School

    Elementary SchoolJember

  5. 2014 — 2017

    Petra 5 Christian Elementary School

    Elementary SchoolSurabaya

  6. 2012 — 2014

    Petra 7 Christian Kindergarten School

    KindergartenSurabaya

  7. 2010 — 2012

    Whiz Kids Play School

    Play School

( Tech stack — 16 tools )

Languages, frameworks & engines

  • Python
  • Swift
  • Julia
  • Java
  • C++
  • HTML5
  • CSS3
  • JavaScript
  • TypeScript
  • GraphQL
  • Kotlin
  • PHP
  • R
  • Ruby
  • Rust
  • Unreal Engine

( Selected work )

Featured projects

10 public & private repos

Featured — 01

WhizReveal

Native Windows raffle controller and audience display built with Tauri, Rust, React, and TypeScript.

TypeScript

Featured — 02

Michelle Farewell

A personal project made with care. Source and details live on GitHub.

JavaScript

Offensive security

Break it first, so no one else can.

All repositories

github.com/ZengLLQ — 08