Mobile Apps Engineer & Game Developer · Jakarta, Indonesia

Mobile apps people rely on.
A game of my own.

I'm William, a Mobile Apps Engineer with 7+ years of experience building high-quality Android apps for e-ticketing, travel, fintech, banking, and music streaming. My apps have more than 20M combined downloads. I'm also the developer behind Rakumaro Game Studio, building a cozy idle RPG on Compose Multiplatform with a game engine I wrote myself.

Download CV (PDF) My game studio
7+
Years of experience
20M+
Combined app downloads
11+
Apps built & shipped
1
Game studio in the making

About

Two hats: mobile engineer, game developer.

I specialize in Native Android (Kotlin/Java) and have cross-platform experience with Flutter. I have strong analytical and debugging skills, and a track record of improving stability, performance, and user experience. My work covers cinema ticketing, travel, and digital banking apps.

Outside of work, I'm building Rakumaro Game Studio, a cozy idle RPG starring a brave little duck. Instead of using Unity or Godot, I write the game engine myself on Compose Multiplatform. Clean, maintainable code matters to me in both worlds.

Get in touch

Skills

What I work with.

Mobile Core

  • Native Android (Kotlin)
  • Java
  • Flutter
  • Compose Multiplatform
  • App size reduction

Architecture

  • MVP
  • MVVM
  • Dependency Injection (Koin)
  • Kotlin Multiplatform
  • Technical debt & code refactor
  • Code review

Quality & Testing

  • Unit testing (JUnit)
  • UI testing (Espresso)
  • Bug-fixing
  • Crashlytics monitoring
  • Complex problem solving

Security

  • Encryption
  • ProGuard
  • Penetration testing (Frida, jadx)
  • App hardening

Game Dev

  • Custom game engine
  • Game systems & loops
  • Idle/incremental design
  • Solo shipping

Languages: Indonesian (native) · English

Experience

Where I've worked.

  1. Jan 2026 – Present

    Android Engineer

    BookCabin · PT Kabin Kita Top (Lion Air Group) · flights & hotels app, 1M+ downloads

    • Developing and maintaining BookCabin's Android app, Lion Air Group's all-in-one travel booking platform for flights and hotels
    • Kotlin
    • Android

  2. Sep 2022 – Dec 2025 · 3 yrs 4 mos

    Android Engineer

    TIX ID · PT Nusantara Elang Sejahtera · cinema ticketing, 10M+ downloads, 4.9★

    • Raised the crash-free rate from 98% to 99.8% via Crashlytics monitoring and quick fixes
    • Developed several TIX ID features for Indonesia's leading cinema ticketing app
    • Built TIX Mini from scratch using Flutter
    • Handled TIX Events merchant offline cashless app
    • Maintained app security and wrote technical documentation
    • Reviewed code and maintained tech debt
    • Kotlin
    • Jetpack Compose
    • Java
    • Flutter
    • Crashlytics

  3. Dec 2020 – Sep 2022 · 1 yr 10 mos

    Android Developer Lead

    PT MNC Bank Internasional, Tbk · digital banking, 1M+ downloads, 4.6★

    • Led a team of 6 engineers and the Android team's biweekly standups
    • Developed several Motion Banking features and improved app security
    • Improved the code structure and team development behavior
    • Mentored junior developers and wrote technical documentation
    • Kotlin
    • Jetpack Compose
    • Koin
    • Encryption
    • ProGuard

  4. Jul 2018 – Dec 2020 · 2 yrs 6 mos

    Android Developer

    PT Code Development Indonesia · client products across fintech, music, marketplace

    • Built, updated, and patched client Android applications, including Langit Musik (10M+ downloads, 4.5★)
    • Delivered products across fintech, sales force, music streaming, and marketplace verticals
    • Java
    • Kotlin
    • Android SDK

Education

Universitas Bunda Mulia · Teknik Informatika, 2016–2020

Game Dev

Rakumaro Game Studio.

In development

A cozy idle RPG starring a brave little duck.

You rest easy, the duck does the fighting. Rakumaro is my own indie studio. The game is an idle RPG where progress never stops, even while you sleep.

Instead of Unity or Godot, I'm building it on Compose Multiplatform with a game engine I wrote from scratch. That gives me full control over the game loop, rendering, and systems.

Follow the journey ↗
Rakumaro, the little duck knight

Portfolio

Apps I've built.

Rakumaro

Cozy idle RPG · in development

Rakumaro Game Studio

  • Compose Multiplatform
  • Custom engine
Visit rakumaro.com ↗

BookCabin

Flights & hotels travel app · current role

PT Kabin Kita Top · Lion Air Group

  • 1M+ downloads
  • Android
  • Kotlin
View on Play Store ↗

TIX ID

Cinema ticketing app

PT Nusantara Elang Sejahtera

  • 10M+ downloads · 4.9★
  • Android
  • Kotlin
  • Java
View on Play Store ↗

Motion Banking

Digital banking app

PT MNC Bank Internasional, Tbk

  • 1M+ downloads · 4.6★
  • Android
  • Koin
  • Security
View on Play Store ↗

Langit Musik

Music streaming app

PT Code Development Indonesia

  • 10M+ downloads · 4.5★
  • Android
View on Play Store ↗

TIX Mini

Ticketing web app

PT Nusantara Elang Sejahtera

  • Flutter
  • Built from scratch
Visit site ↗

TIX Events POS App

Offline cashless merchant POS

PT Nusantara Elang Sejahtera

  • Android
  • Offline-first
Internal app

Watervall

Fintech app

PT Code Development Indonesia

  • Android
Internal app

Apollo & Monica

Sales force apps

PT Code Development Indonesia

  • Android
Internal apps

Merapi

Sales force application

PT Code Development Indonesia

  • Android
Internal app

CloseBuy

Map-based property marketplace

PT Code Development Indonesia

  • Android
  • Maps
Delisted

Aduk-aduk Poin Berhadiah

Loyalty member app

PT Code Development Indonesia

  • Android
Delisted

Ratings as of 2025, during my time on the teams.