John Ernest Guadalupe, Developer in Parañaque, Philippines
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John Ernest Guadalupe

Verified Expert  in Engineering

Android Developer

Parañaque, Philippines
Toptal Member Since
December 18, 2015

John prioritizes delivering value. He proactively discusses the system architecture to develop an intuitive, user-friendly, and developer-friendly product. John is passionate about bringing disruptive ideas to the market and providing top-tier business-specific requirements.


Orion180 Insurance Services LLC
Xamarin, .NET, C#, JavaScript, HTML, CSS, Databases, Mobile UI, Full-stack, SQL...
React Native, Kotlin, Android, AngularJS, Xamarin.Forms, Microsoft SQL Server...
Freelance Work
Android, Technical Leadership, Android SDK, Kotlin, RxAndroid, C#, GraphQL...




Preferred Environment

Android Studio, Visual Studio, Visual Studio Code (VS Code), Azure, Firebase

The most amazing... I've made is an NFT centric application with real-time data, tools, alerts, and utility for the holders.

Work Experience

Hybrid Mobile Insurance Application Developer

2021 - PRESENT
Orion180 Insurance Services LLC
  • Pioneered application development, implementing features found on the web app using the same back end.
  • Implemented user interface designs using Xamarin Forms. Customized controls and views depending on the need per platform. Customized behaviors and interface for feature implementation.
  • Maintained the application by fixing bugs, implementing adjustments, and adding new features needed as per business requirements and continuity.
Technologies: Xamarin, .NET, C#, JavaScript, HTML, CSS, Databases, Mobile UI, Full-stack, SQL, Azure, Bootstrap, Vue, REST APIs, SourceTree, API Integration, UI Design, UX Design, Mobile Apps, APIs, Design, .NET MAUI, Google Play Console, Testing, Security, JSON, Mobile Development, WebView, User Experience (UX), User Interface (UI)

Mobile Developer Senior Consultant II

2020 - PRESENT
  • Guided clients on the technical aspects of their projects.
  • Assisted teams in multiple mobile projects, being the lead developer on several projects.
  • Developed software for multiple projects spanning mobile and web technologies.
  • Served as a full-stack developer building mobile and web applications. I also maintained existing apps for bug fixes and new feature integration.
Technologies: React Native, Kotlin, Android, AngularJS, Xamarin.Forms, Microsoft SQL Server, Azure, .NET, Android SDK, RxAndroid, C#, Xamarin, Technical Leadership, Software Architecture, Google API, SourceTree, Retrofit 2, RxJava, React, Firebase, TypeScript, API Integration, Chatbots, UI Design, UX Design, Mobile Apps, APIs, Design, Expo, Google Play Console, Geolocation, Testing, Security, JSON, Spring Boot, Mobile Development, MySQL, HTML5, WebView, Amazon Web Services (AWS), .NET MAUI, User Experience (UX), User Interface (UI), Angular

Software Architect and Lead Developer

2013 - PRESENT
Freelance Work
  • Developed applications from the ground up, following the appropriate methodologies for software development for corporate and public use.
  • Studied and implemented different paradigms as case studies for different projects to know the best ones for different niches.
  • Utilized multiple leading technologies for features such as location, maps, payments, user experience, analytics, and behavior patterns.
  • Led teams, set project deadlines, and worked as part of teams for different projects.
  • Used Google Sheets, Docs, and Slides to keep teams on track.
  • Communicated directly and promptly with the client about any concerns regarding the project.
  • Implemented Material Design principles on different projects.
Technologies: Android, Technical Leadership, Android SDK, Kotlin, RxAndroid, C#, GraphQL, Software Architecture, Google API, Firebase Realtime Database, SourceTree, Retrofit 2, RxJava, Cloud Firestore, Xamarin, React, React Native, Node.js, TypeScript, API Integration, UI Design, UX Design, Mobile Apps, APIs, Design, Google Play Console, Geolocation, Stripe API, Testing, Security, JSON, Mobile Development, HTML5, WebView, Algolia, User Experience (UX), User Interface (UI)

Mobile Developer

2022 - 2023
10 Gears LLC
  • Implemented a new server instance with automated publishing of the back-end server from a GitHub Action.
  • Managed Android and iOS mobile apps and admin web app code repositories for new feature implementations.
  • Led and integrated new database instances for the revamped back end.
Technologies: iOS, Mobile Payments, Android, Swift, Java, Kotlin, Android SDK, iOS SDK, React, Express.js, Node.js, GitHub, API Integration, Mobile Apps, Google Play Console, Geolocation, Testing, JSON, Mobile Development

Senior Native (Apple and Android) Developer

2022 - 2022
Imagemakers Inc.
  • Used Jira software for tracking tickets and maintaining applications by fixing bugs, adjusting behaviors, and fixing layouts.
  • Utilized JavaScript in analyzing and mitigating bugs on the web app.
  • Monitored the application performance, adjusting variables and logic as necessary.
Technologies: Android, iOS, Swift, Java, JavaScript, PostgreSQL, jQuery, Vanilla JS, Google API, SourceTree, API Integration, Mobile Apps, Google Play Console, Testing, JSON, Mobile Development

Senior Mobile Developer

2018 - 2020
Navitaire Philippines, Inc. (via NTT Data Philippines)
  • Maintained existing airline applications for customers developed using Xamarin Forms.
  • Fixed bugs on both Android and iOS platforms using C#.
  • Developed new features involving RESTful services, Xamarin Forms, and C#.
Technologies: GraphQL, Android, C#, Xamarin, Android SDK, Kotlin, Xamarin.Forms, Technical Leadership, Software Architecture, Google API, SourceTree, API Integration, Mobile Apps, Google Play Console, Geolocation, Testing, JSON, Mobile Development

Senior Android Developer

2016 - 2018
Inovotek Apps, Inc.
  • Led the Android team in the implementation of new features to existing projects.
  • Maintained existing projects, including handling release and bug monitoring.
  • Discussed and implemented the architecture foundations for projects with iOS, web, and design team leaders.
Technologies: Crashlytics, Jira, Bitbucket, Technical Leadership, Android, Java, Android SDK, Kotlin, RxAndroid, Software Architecture, Google API, Firebase Realtime Database, SourceTree, Retrofit 2, RxJava, Cloud Firestore, API Integration, Mobile Apps, Google Play Console, Geolocation, Stripe API, Testing, JSON, Mobile Development

Senior Android Developer

2016 - 2016
Samsung Mobile R&D Philippines
  • Spearheaded the Espresso implementation in projects.
  • Maintained existing applications by fixing bugs, adjustments, and aesthetics.
  • Implemented new features such as email automation on mobile apps and recognition of content.
Technologies: Jira, GitHub, Spoon Testing, Espresso, Eclipse, Xamarin, Android, Java, Android SDK, Software Architecture, SourceTree, RxJava, API Integration, Mobile Apps, Google Play Console, Testing, JSON, Mobile Development

Software Developer

2013 - 2016
KLab Cyscorpions, Inc.
  • Developed new features on existing apps. Maintained applications by adding new modules on existing features and/or creating a new module from scratch.
  • Resolved app issues by utilizing issue-tracking technologies.
  • Code-reviewed pull requests to maintain the quality of code.
  • Pioneered the usage and development of a unit testing framework using Robotium.
  • Supported, taught, and led junior developers with multiple tasks.
  • Helped with improvement and implementation of the current workflow.
Technologies: Spoon Testing, GitHub, Robotium, Eclipse, Android, Java, Android SDK, Software Architecture, Firebase Realtime Database, SourceTree, Retrofit 2, RxJava, API Integration, Mobile Apps, Google Play Console, Testing, JSON, Mobile Development


A delivery platform where users can order from markets, restaurants, pharmacies, and other store categories. It utilizes Google Maps for location features and has an intuitive design that appeals to the younger market.

I have led the software development team in this project, managing at most 10 people comprised of Android, iOS, and web developers, as well as QA engineers and business analysts. We have used Firebase for the authentication, database, hosting, and analytics. We have also used Stripe for the payments.

I have also led the development of the Android app utilizing Kotlin. I have used the MVVMC architecture using Conductor for the controller and navigation stack, Dagger for dependency injection, Kotlin Coroutines for multi-threading, and Android architecture components such as ViewModel and LiveData.

Tarjemle | Translation Services

I led the development of this platform for translators. With agile practices already in place, I planned the architecture and development schedule of multiple web portals and Android and iOS applications, as well as landing pages and back-end servers.

I also personally developed the Android application for customers and translators here, wherein they can have documents analyzed and have words automatically counted.

Translators can accept and decline tasks. Both the customers and translators can coordinate with account managers for the tasks and results through the chat module (that we developed). We used Firebase Firestore for the applications' back end.

Pulire | Shoe Cleaning Service
Pulire is a service to have all kinds of shoes cleaned. It has a menu for the services you can avail of and where you'd like the shoes picked up and delivered. It has a partner app for its couriers, which I also developed. I collaborated with a team I have handpicked to create a working, commercial system complete with an admin portal.

The customer can create an order to upload pictures of a pair of shoes that need servicing and the specific services he wants. After the shop's couriers are notified and accept the pickup request, the app gives them the customer's location. The couriers then collect the items and payments. Once the shoes have arrived at the store, an admin monitors the cleaning process, prompts user updates, and users get notified through push notification. After the service is completed, the shoes will be delivered back to the customer.

PharmacyDirect | A Medicine Delivery System
With one of my developer friends, we created a suite of applications for a company that delivers medicine to people in South Africa.

I created the client and the delivery personnel applications.

The client application allows users to upload prescriptions and update them about concerning their deliveries, which are automatically managed by the system. It also shows them the current location of the personnel that is delivering the medicine.

For the delivery personnel app, it was designed to give the users notifications when a delivery is assigned to them as well as show the location of the client.

BaryaCard | Financial App

This app is a financial app that aims to help Filipinos save money when buying from convenience stores, food stands, etc. Instead of getting the coin change right then and there, they can choose to have it deposited into their BaryaCard account. Currently, two companies have partnered with BaryaCard so that they can offer the services within the app and be part of the profit-sharing model that my clients have envisioned.


Mister Donut —

InkMyPapers | Assignment Help

InkMyPapers is a service where students can ask for help on their essays, dissertations or presentations. I created and managed a team that will develop a multitude of apps where I developed the Android app myself.

Shawer App | eLaw App

Shawer is an eLaw application that connects lawyers with potential clients. It is an online legal services marketplace connecting consumers and lawyers across the region. Shawer app is not a law firm in of itself and doesn’t provide any legal services; it merely facilitates the connection of lawyers and clients.

Shawer users can purchase in-app currency via the Google Play and the Apple App Store and after purchase can access the available services of various lawyers and services ranging from consultations to legal representation in court.

DURA LEX | Social Italian and European Law Application

DURA LEX is a new kind of application that aims to bring social functions to a repository of Italian and European laws. It will also have powerful searching capabilities that enable users to search for resolutions and judgments to legal court cases. Currently, it is in development.

Appily | A Journal App with a Personality Analysis

I developed a journal app that has an automatic data synchronization with the back end, a Google Drive backup, a personality analysis, and a customized feedback logic. It was also implemented with Material Design so that it is compatible up to API 15.

Paloma Forum App

This project allows employees of an existing company to communicate and share information through a mobile app. The user can enter posts, categorize, send files, and collaborate on forum postings and edit material.

This is a blogging app that I made for an existing blogging platform. All the designs were made by the designer and I implemented them pixel by pixel. Aside from the features shown in the video, it also has push notifications for news, reminders, and more.


The app functions like Uber but caters to motorcycle drivers in the Philippines. The app shows the location, creates routes and maps, and lets users see the estimated arrival time and duration to gauge travel properly. The app allows drivers to receive bookings and track their history of travel.


An app focusing on delivering analytics on NFTs based on different sources such as, NFTPort, and others. I collected data and created an attractive UI for displaying data on charts and bar charts. I also provided predictions for proper NFT staking, buying, and selling.

Basketball League Application

A React Native-based application that aims to make the organization and completion of leagues between teams with small to medium followings in neighborhoods easier and more secure. Features include the creation of leagues with maps, location setting, player selection, contract creation and bet holding and assistance, and team management.

Vehicle Dealership Management App

A React Native application that is based on an existing web application used to manage the inventory and business of dealerships across the US. Features include VIN code scanning and OCR, inventory management, listing management, and more
2009 - 2013

Bachelor's Degree in Computer Science

Technological University of the Philippines - Manila, Philippines


Node.js, Android Support Library, Retrofit 2, RxJava, Google API, Twitter SDK, Facebook SDK, React, REST APIs, Stripe API, Google Maps API, jQuery, Vue


Bitbucket, SourceTree, RxAndroid, Android Jetpack, Expo, WebView, Jira, Crashlytics, Visual Studio, GitHub


React Native, AngularJS, Android SDK, .NET MAUI, Angular, .NET, Espresso, Robotium, ORMLite, Vanilla JS, Bootstrap, iOS SDK, Express.js, Spring Boot


TypeScript, Kotlin, Java, C#, HTML5, JavaScript, GraphQL, Swift, HTML, CSS, SQL, C#.NET


Model View Presenter (MVP), Agile Software Development, UI Design, UX Design, Testing, Mobile Development, Unit Testing, Spoon Testing


Firebase, Android, Xamarin, Algolia, iOS, Windows, Eclipse, Mobile, Azure, Visual Studio Code (VS Code), Amazon Web Services (AWS)


Firebase Realtime Database, Cloud Firestore, JSON, MySQL, Microsoft SQL Server, PostgreSQL, Databases


Technical Leadership, Google Material Design, Google+ Authentication, EventBus, API Integration, Mobile Apps, APIs, Design, Google Play Console, Geolocation, Security, User Experience (UX), User Interface (UI), OCR, Xamarin.Forms, Software Architecture, Mobile UI, Full-stack, Mobile Payments, Chatbots

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