About

Hello! I'm Hangga Aji Sayekti, a former math teacher turned software engineer and technical author. My journey from education to technology has fueled my passion for creating accessible and inclusive digital experiences.

I started coding in 2008 as a Delphi programmer before moving to web development in 2010, where I discovered my first authorization and IDOR bugs. That experience sparked my long-term interest in cybersecurity.

Over the years, I’ve worked across Android, iOS, and data engineering, eventually leading development teams. These roles gave me a broader view of how software, data, and security connect in real projects.

Since 2023, I’ve been writing for Baeldung and later joined the CircleCI Blog as a contributor and technical reviewer. In 2025, I started contributing to Linux Handbook with a series on pentesting, while spending my free time sharpening my bug hunting skills.

Experience

  1. May 2025 — Present

    CircleCI

    Technical Code Reviewer

    San Francisco | Remote | Freelance

    Reviewed technical tutorials for the CircleCI blog by testing code samples, verifying successful builds, ensuring content clarity, and maintaining consistency with editorial standards. Collaborated with authors to resolve issues and published verified repositories.

    • Markedown
    • CI/CD
    • Git
    Feb 2025 — Present

    Technical Author

    San Francisco | Remote | Freelance

    I create content at CircleCI about CI/CD automation, security testing, and performance tuning — from adding vulnerability scans to pipelines to speeding up Kotlin coroutines and automating API security tests in Java.

    • Java
    • Kotlin
    • CI/CD
    • Security
    • Git
  2. Aug 2023 — Feb 2025

    Kredibel

    Head of Product & Engineering

    Jakarta - Indonesia | Remote | Fulltime

    • R&D for new feature ideas based on company and user needs.
    • R&D for new tech/library implementation needed.
    • Solving problems regarding application releases: Google Play Store and Apple Store.
    • Still working as a software engineer. 😁
    Sep 2020 — Feb 2025

    Sr. Software Engineer | Mobile

    Jakarta - Indonesia | Remote | Fulltime

    • Develop mobile apps from scratch (Android & iOS).
    • Develop Kredibel Vision SDK (Android).
    • Manage Kredibel Remote Maven Repository.
    • R&D for new tech/library implementation needed.
    • R&D for some ML libraries for mobile platforms such as Google ML Kit, Firebase ML Kit, Huawei ML Kit, etc.
    • Create prototypes for demo to clients/users if needed.
    • Java
    • Kotlin
    • Android Studio
    • RxJava
    • Retrofit
    • Firebase
    • GitLab
    • ML Kit
    • Xcode
    • Swift
    • SwiftUI
    • Alamofire
    • SwiftyJSON
    • CoreData
    • Maven Repository
    • Repsy.io
    • Microsoft Azure DevOps
    • Google Artifact Registry
  3. Aug 2015 — Mar 2020

    Sebangsa Network

    Team Lead

    Yogyakarta - Indonesia | OnSite | Fulltime

    • Responsible for teamwork, from development, testing, bugfixing, staging to release/production.
    • Review, motivate, guide, and help the team solve problems if they have difficulties.
    • Schedule new technology research as needed and determine whether to implement it or not.
    • Android Studio
    • Java
    • RxJava
    • Retrofit
    • OkHttp
    • JSON
    • Gson
    • Firebase
    • Dagger
    • MVP
    • GitLab
    • Subversion
    • Google Play Console
    Aug 2015 — Aug 2017

    Sr. Android Developer

    Yogyakarta - Indonesia | OnSite | Fulltime

    • Mentoring junior.
    • R&D for new tech/library implementation needed.
    • Contribute to Sebangsa, Arena, and “Q” projects.
    • Android Studio
    • Java
    • Retrofit
    • OkHttp
    • JSON
    • Gson
    • GCM
    • MVP
    • GitLab
    • Subversion
    Jan 2013 — Aug 2015

    Android Developer

    Yogyakarta - Indonesia | OnSite | Fulltime

    Develop Sebangsa apps from scratch. Responsible for coding, testing, bug fixing, staging, and release/production.

    • Android Studio
    • Java
    • Retrofit
    • OkHttp
    • JSON
    • Gson
    • GCM
    • MVP
    • GitLab
    • Subversion
  4. Mar 2010 — Dec 2012

    Puskom UNY

    Web Programmer

    Yogyakarta - Indonesia | OnSite | Fulltime

    • Student Registration.
    • Financial Monitoring.
    • Speedy internet services.
    • SitungRek (for rector candidate vote count).
    • Number of websites for some seminar, scientific event, or workshop.
    • Assisting IT training mentors for lecturers and staff.
    • Help support IT for every campus event.
    • Delphi 7
    • PHP
    • CodeIgniter
    • CSS
    • HTML
    • jQuery
    • MySQL
    • PostgreSQL
    • WebService
    • SOAP
  5. Jun 2008 — Nov 2010

    CV. Solusi Netindo

    Desktop App Developer

    Yogyakarta - Indonesia | OnSite | Parttime

    Develop apps for Windows platform such as Management Information Systems, Inventory System, Airline Ticketing Systems and Ship Port Information System.

    • SQL
    • Microsoft SQL Server
    • Delphi
    • Firebird
    • InterBase SQL
    • VCL
  6. 2003 — 2004

    CV. Mutiara Tiga Prima

    Layout Editor

    Yogyakarta - Indonesia | OnSite | Parttime

    • Layout editing using Corel Draw 11.
    • Print to Plate.
    • Print Mirror.
    • Print to tracing paper (kalkir).
    • Deliver printed script to Machine Operator.
    • Help finishing if needed.
    • Corel Draw 11
View Full Résumé

Projects

  • Spotify Profile

    Kredibel Vision SDK

    Vision SDK is a library that provides computer vision services such as Liveness Detection and Identity OCR with Kredibel VisionAI technology.

    • Java
    • Kotlin
    • Kredibel API
    • Machine Learning (ML)
    • Modularization
    • Maven
    • Repsy.io
  • Halcyon Theme

    CIH - Cheapest Insertion Heuristic Algorithm

    Asymmetric Traveling Salesman Problem With Cheapest Insertion Heuristic Algorithm, Th.2009. Proyek penelitian bidang studi Matematika Universitas Negeri Yogyakarta.

    • Pascal
    • Delphi
    • Firebird
  • Kredibel – Cek Penipu Online

    Kredibel Android

    Kredibel is a startup tackling fraud and trust issues, helping people avoid scams and businesses build trust, comply with regulations, and reduce fraud.

    • Java
    • Kotlin
    • RxJava
    • Retrofit
  • Kredibel – Cek Penipu Online

    Kredibel iOS

    Kredibel is a startup tackling fraud and trust issues, helping people avoid scams and businesses build trust, comply with regulations, and reduce fraud.

    • Swift
    • SwiftUI
    • Alamofire
    • SwiftyJSON
    • CoreData
  • Halcyon Theme

    UsaidBox

    Usaidbox is lightweight embedded PDF preview in Swing GUI

    • Java
    • Swing
    • Apache PDFBox
  • Halcyon Theme

    Sebangsa App

    Sebangsa.com is a community social marketplace platform. In March 2016, Sebangsa, a social media platform for Indonesian communities, was selected as one of the National OTTs.

    • Java
    • RxJava
    • MVP
    • GCM
    • Firebase
    • Google Analytics
View Full Project Archive

Writing

View more... Baeldung CircleCI Blog Linux Handbook Blog

teaching

  1. Apr 2021 — Jun 2021

    FMIPA - Universitas Negeri Yogyakarta

    Guest Practitioner Lecture · Mobile Application Development

    Yogyakarta - Indonesia | Seasonal

    Workshop on mobile application development, in order to improve learning and conformity with the industrial world and the meaning of “Kampus Merdeka”.

    • Android Studio
    • Java
    • Kotlin
    • SQLite
  2. Oct 2016

    SMK Ibu Pawiyatan Tamansiswa

    Instructor Kelas 9 Belajar Bareng Sebangsa

    Yogyakarta - Indonesia | Seasonal

    Talk about : Membuat Aplikasi Mobile Android Keren.

    • Android Studio
    • Java
  3. Jun 2015 — Dec 2015

    Pondok Programmer

    Mentors

    Yogyakarta - Indonesia | OnSite

    Teaching and making a syllabus, include material and sample project. Monitoring the increased ability and and giving consultation of students.

    • Java
    • Eclipse IDE
    • Android SDK
    • XML
    • Layouting
    • Motion animation
    • Basic Game Development
  4. 2003 — 2007

    Math Teacher · Self-employed

    Yogyakarta - Indonesia | Freelance

    Teaching Mathematics privately for Elementary and Junior High School students.

    • Numbers & Operations
    • Fractions & Decimals
    • Basic Algebra
    • Geometry
    • Ratio & Proportion
    • Pythagoras Theorem
    • Problem Solving
  5. 2008 – 2009

    SMP Muhammadiyah 9 Yogyakarta

    Teacher of Tilawatil Qur’an - Extracurricular Lessons

    Yogyakarta - Indonesia

    • Teaching Qur'an with Tartil, Mujawwad, and Nagham with 7 maqamat.
    • Intensive lessons for students to prepare for the Musabaqah Tilawatil Qur'an (MTQ) competition.
    • Intensive lessons for students as qori' to prepare for Islamic holidays and other events.
  6. 2000 – 2004

    Taman Pendidikan Al-Qur’an Fastabiqul Khairat

    Qur'an Teacher

    Yogyakarta - Indonesia

    Teaching Iqra, Qur’an, Tartil, Tajwid and Kitabah.