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Senior Android Engineer with 8+ years of experience building and scaling mobile applications across fintech, edtech, and media. Proven ability to take ownership of complex legacy and greenfield codebases—refactoring monoliths, architecting reusable systems, and mentoring engineers. Strong expertise in Kotlin, Jetpack Compose, and Clean Architecture, complemented by hands-on work across backend, frontend, and data layers. Comfortable working in fast-paced, English-speaking, cross-functional teams (4 to 50+ engineers) across Brazil, Portugal, Indonesia, and the US. Worked on large-scale international projects for organizations such as PayPal, Snapchat, and XP Investments, delivering high-quality features with strong test coverage and observability.…Senior Android Engineer with 8+ years of experience building and scaling mobile applications across fintech, edtech, and media. Proven ability to take ownership of complex legacy and greenfield codebases—refactoring monoliths, architecting reusable systems, and mentoring engineers. Strong expertise in Kotlin, Jetpack Compose, and Clean Architecture, complemented by hands-on work across backend, frontend, and data layers. Comfortable working in fast-paced, English-speaking, cross-functional teams (4 to 50+ engineers) across Brazil, Portugal, Indonesia, and the US. Worked on large-scale international projects for organizations such as PayPal, Snapchat, and XP Investments, delivering high-quality features with strong test coverage and observability.

Willi Guillerme Rittmann

Software Engineer, App Developer, Back-End Developer, +1

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Senior Android Engineer with 8+ years of experience building and scaling mobile applications across fintech, edtech, and media. Proven ability to take ownership of complex legacy and greenfield codebases—refactoring monoliths, architecting reusable systems, and mentoring engineers. Strong expertise in Kotlin, Jetpack Compose, and Clean Architecture, complemented by hands-on work across backend, frontend, and data layers. Comfortable working in fast-paced, English-speaking, cross-functional teams (4 to 50+ engineers) across Brazil, Portugal, Indonesia, and the US. Worked on large-scale international projects for organizations such as PayPal, Snapchat, and XP Investments, delivering high-quality features with strong test coverage and observability.…Senior Android Engineer with 8+ years of experience building and scaling mobile applications across fintech, edtech, and media. Proven ability to take ownership of complex legacy and greenfield codebases—refactoring monoliths, architecting reusable systems, and mentoring engineers. Strong expertise in Kotlin, Jetpack Compose, and Clean Architecture, complemented by hands-on work across backend, frontend, and data layers. Comfortable working in fast-paced, English-speaking, cross-functional teams (4 to 50+ engineers) across Brazil, Portugal, Indonesia, and the US. Worked on large-scale international projects for organizations such as PayPal, Snapchat, and XP Investments, delivering high-quality features with strong test coverage and observability.

Available to hire

Senior Android Engineer with 8+ years of experience building and scaling mobile applications across fintech, edtech, and media. Proven ability to take ownership of complex legacy and greenfield codebases—refactoring monoliths, architecting reusable systems, and mentoring engineers. Strong expertise in Kotlin, Jetpack Compose, and Clean Architecture, complemented by hands-on work across backend, frontend, and data layers.

Comfortable working in fast-paced, English-speaking, cross-functional teams (4 to 50+ engineers) across Brazil, Portugal, Indonesia, and the US. Worked on large-scale international projects for organizations such as PayPal, Snapchat, and XP Investments, delivering high-quality features with strong test coverage and observability.

Skills

Experience Level

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Intermediate

Intermediate

Language

Portuguese

Fluent

English

Advanced

Work Experience

Android Engineer (allocated to XP PayPal) at Thaloz

July 1, 2024 - June 30, 2026

Designed and built a Jetpack Compose dynamic, GraphQL-driven form system that renders fields, validation rules, input masks, and field interdependencies at runtime from a single UI state object, eliminating one-off forms across the module. Created the “payment-form at-change” flow from scratch, including a complete address flow (form, search, edit) as part of a loan and internationalization initiative. Worked on migrating the module from legacy architecture to MVI + Compose during a company-wide migration from multiple repositories into a single monorepo, contributing shared utilities and optimizations. Implemented internationalization abstraction layers enabling per-country injection across the app. Worked exclusively with GraphQL/Apollo (no REST), maintaining 85%+ test coverage and using Datadog for observability and Jenkins for CI/CD in an Agile/Scrum environment.

Freelance Android Engineer at Freelance (EdTech startup in Indonesia)

May 1, 2023 - June 30, 2024

Sole Android developer for an EdTech startup in Indonesia, rebuilding a legacy teacher-booking/scheduling platform from scratch. Owned the end-to-end mobile architecture, modularization strategy, requirements gathering, and key UI/UX decisions while working in a fully English-speaking remote team. Learned JNI from scratch to integrate a C/C++ layer as one of the data sources behind the repository layer. Built a complex Jetpack Compose scheduling screen with an infinite-scroll calendar including zoom and navigation by date/month/year. Researched and integrated a non-Google map pinning API due to budget constraints, implementing custom map tiling and rendering. Identified and raised scope and process issues (uncontrolled scope creep and unjustified technical decisions) to project leadership.

Android Engineer (allocated to Snapchat Android Quality Engineering team) at Capgemini Portugal

October 1, 2022 - March 31, 2023

Wrote automated integration tests for one of the world’s largest social media apps, including advertising-related features, maintaining ~80% test coverage. Adopted the Page Object pattern for the first time, improving test readability and maintainability (still in use). Collaborated in a mixed local/remote setup, syncing daily in English with US-based management.

Android Engineer (Android TV streaming platform) at Aubay Portugal

May 1, 2022 - October 1, 2022

Delivered UI fixes and a lightweight caching system for one of the most complex, heavily customized codebases in the company portfolio, deliberately using minimal external libraries to fit Android TV constrained resources. Ramped up through extensive internal documentation and code history to safely contribute to a mature, high-stakes production application.

Android Engineer (allocated to XP Investments) at GFT Brazil

July 1, 2021 - May 31, 2022

White-label mobile platform powering multiple XP Investments brands (Ricco, Clear, and others) using shared, tokenized UI libraries. Contributed to a shared component/flow library, including a reusable Login SDK consumed across multiple production apps, each customized via style and a tokenization system. Worked in 100% pair programming, rotating roles with less senior developers and documenting every session using a workflow designed to offset ~8-hour build times. Wrote extensive unit tests (MockK, JUnit) and gained hands-on exposure to Bazel as an alternative build system to Gradle.

Android Engineer (allocated to GerenciaNet) at UseMobile

November 1, 2020 - June 30, 2021

Worked on a large Brazilian fintech platform within a cross-platform module team (Android + iOS). Delivered Cards management and Pix payment integration features within an existing Clean Architecture codebase; contributed camera/QR code flows and resolved recurring performance animation issues. First experience working in a dedicated feature module inside a large project (~20 people) with daily standups and structured sprints.

Android Engineer at Trinity Soluções

November 1, 2018 - October 31, 2020

Took ownership of the company’s flagship sales app, a large legacy codebase with no tests and multiple “god classes”—refactoring core systems, removing dead code, and introducing the project’s first functional UI tests (Espresso). Resolved a high volume of bugs in the first 30 days. Took over a greenfield Kotlin truck logistics app after the team’s senior developer left, implementing CameraX (new at the time) and solving device-compatibility issues across 20+ Android devices. Recruited, onboarded, and mentored an intern with no prior Kotlin experience, architecting an offline-first field service MVP (photo capture, background sync) delivered ahead of schedule. Promoted multiple times over ~2 years, from trainee to de facto technical owner of the main product, training other engineers to help maintain it.

Android Development Intern at JBR Engineering

July 1, 2017 - April 30, 2018

Built two field-data Android apps from scratch for a civil engineering firm with no existing dev team: a truck-counting tool with manual CRUD and structured Excel export, and a lane-damage assessment tool combining custom drawing layers with Excel-integrated reporting; both fully offline. Also built a Chrome extension to automate a printer workflow on request.

Web/Mobile Development Intern at PSD Digital Agency

February 1, 2017 - May 31, 2017

Built a pet management app from scratch using Ionic 2 and Node.js, first mobile project while maintaining legacy JavaScript codebases, including a SaaS product.