Andrzej is available for hire
Hire AndrzejAndrzej Chmielewski
Verified Expert in Engineering
iOS Developer
Wrocław, Poland
Toptal member since January 19, 2017
Bio
Andrzej is a seasoned mobile developer with 10 years of experience in native app development for Android and iOS and three years in Flutter. He's skilled at building apps from scratch, proposing robust architectures, and leading teams. He follows a test-driven or behavior-driven development (TDD/BDD) approach and has extensive experience in unit and integration testing. Andrzej is also experienced in building sophisticated CI/CD pipelines for the timely delivery of high-quality apps.
Portfolio
Uber Carshare
Flutter, Android, iOS, Mobile App Development, Fastlane, Xcode, NoSQL...
On
Flutter, Mobile Architecture, Mobile Apps, MacOS, Full-stack, Fastlane, Xcode...
Picnic
Flutter, Team Leadership, Leadership, GraphQL, CI/CD Pipelines, GitHub, Android...
Experience
- iOS - 10 years
- Android - 10 years
- Mobile - 7 years
- Mobile Architecture - 6 years
- Full-stack - 6 years
- Flutter - 5 years
- Clean Architecture - 5 years
- Dart - 3 years
Preferred Environment
MacOS, GitHub, Git, Android Studio, IntelliJ IDEA
The most amazing...
...thing I've accomplished is being featured twice on Androidweekly.net for articles and open-source libraries I've created.
Work Experience
Senior Flutter Developer
2023 - PRESENT
Uber Carshare
- Helped develop a Flutter app to run on native mobile devices and a web project to run inside the main Uber app.
- Squashed tricky bugs as an expert in the Flutter framework.
- Optimized the performance of the Flutter web app to run in a limited environment of the web view inside the Uber app.
Technologies: Flutter, Android, iOS, Mobile App Development, Fastlane, Xcode, NoSQL, Mobile Architecture
Flutter Architect
2024 - 2025
On
- Led the development of a macOS and iPad sales app responsible for 60% of the company's revenue.
- Designed a scalable Clean Architecture and implemented offline-first support using ObjectBox.
- Built CI/CD pipelines from scratch with Bitrise and GitHub Actions to automate builds, tests, and deployments.
- Optimized app performance by reducing load times and offloading heavy computations to background threads.
Technologies: Flutter, Mobile Architecture, Mobile Apps, MacOS, Full-stack, Fastlane, Xcode, SQLite, NoSQL
Head of Mobile
2022 - 2023
Picnic
- Translated business requirements into actionable tasks and managed a team of 16 Flutter developers.
- Outlined the architecture and working environment for the Picnic app.
- Specified sophisticated and advanced CI/CD pipelines to streamline the development process.
- Optimized performance and maintained high-quality standards for the mobile app.
Technologies: Flutter, Team Leadership, Leadership, GraphQL, CI/CD Pipelines, GitHub, Android, iOS, MacOS, Mobile Architecture, Mobile App Development, Social Media Apps, PostgreSQL, Tailwind CSS, Python, Full-stack, Fastlane, Xcode, SQLite, NoSQL
Android and iOS Mobile Developer
2018 - 2023
Ease (formerly EaseCentral)
- Wrote an Android app from scratch based on the existing iOS version using Kotlin.
- Refactored the entire iOS application to incorporate clean architecture paradigms and code with Swift.
- Initiated instrumented tests for Android and iOS using Espresso for Android and EarlGrey and XCUITest for iOS.
- Integrated Fastlane for an iOS and Android project to help build a working continuous integration solution.
- Introduced unit tests for Android and iOS applications.
- Built custom Gradle scripts to allow easier execution for the Android app's continuous integration pipeline.
Technologies: Mobile, Android SDK, Android Testing, Android, iOS, Swift, Kotlin, Test-driven Development (TDD), Firebase Test Lab, Model View Presenter (MVP), Clean Architecture, Clean Code, APIs, Mobile Development, REST, Architecture, Mobile Architecture, Mobile App Development, Fastlane, Xcode, SQLite, Full-stack
Flutter Developer
2021 - 2022
OK Future
- Refactored an existing app to adhere to clean architecture principles.
- Introduced various quality assurance tools, like screenshot testing, continuous integration, and code coverage.
- Implemented new features and released new versions of the Asphaltgold app.
Technologies: Flutter, Firebase Test Lab, GraphQL, TypeScript, Model View Presenter (MVP), Clean Architecture, Clean Code, APIs, Mobile Development, Architecture, Mobile Architecture, Mobile App Development, Fastlane, Xcode, NoSQL
Mobile Tech Lead
2021 - 2022
Tendermint
- Outlined the architecture and implemented open-source tools for mobile app development based on Cosmos SDK blockchains.
- Managed a team of two other mobile developers, mentoring and guiding the direction of the technical aspect of the product.
- Built a mobile wallet app to manage cryptocurrency assets on the Cosmos Hub blockchain.
Technologies: Team Leadership, Technical Leadership, Flutter, Firebase Test Lab, Model View Presenter (MVP), Clean Architecture, Clean Code, APIs, Mobile Development, Architecture, Mobile Architecture, Mobile App Development, Fastlane, Xcode, NoSQL, Full-stack
Android Developer
2020 - 2021
Groomer.io
- Developed an Android app for pet grooming shop management.
- Introduced unit and integration tests using screenshot testing and Espresso framework.
- Introduced CI/CD services to the development process.
Technologies: Android, Kotlin, APIs, Mobile Development, REST, Architecture, Mobile Architecture, Mobile App Development, Xcode
Flutter Developer
2020 - 2020
Vid, Inc. (via Toptal)
- Created video processing functionalities in Flutter, targetting both iOS and Android. Video processing included: Encoding videos, trimming, and applying separate audio streams from the audio files.
- Introduced new functionalities into the Flutter project as well as existing ones, making sure all of them work well on iOS and Android.
- Helped the team to promptly deliver the Android counterpart written in Flutter based on the existing iOS native app.
Technologies: Mobile, Video & Audio Processing, Video Processing, iOS, Android, Videos, Flutter, Test-driven Development (TDD), Firebase Test Lab, Model View Presenter (MVP), APIs, Google Maps API, Mobile Development, REST, Mobile App Development, Xcode
Flutter Developer
2020 - 2020
Juno Digital Pte., Ltd. (via Toptal)
- Created a lottery results app in Flutter from scratch for both Android and iOS.
- Built a store listing on Google Play and the App Store and conducted the release process.
- Added crash reporting functionalities with Crashlytics to the Flutter project and monitored the app's performance and health to prevent bad user experience.
Technologies: Mobile, iOS, Android, Flutter, REST APIs, Test-driven Development (TDD), Firebase Test Lab, Model View Presenter (MVP), APIs, Mobile Development, Mobile App Development
Android Developer
2019 - 2020
Dubsmash (via Toptal)
- Introduced new features in a video social media app with over 100 million downloads.
- Participated in a mature and well-organized scrum process.
- Helped transition the Java source code into Kotlin.
- Contributed to the redesign of the outdated user interface.
- Augmented the current continuous integration setup with custom scripts that automated tedious, repetitive tasks.
Technologies: Mobile, Android SDK, Android Testing, GraphQL, Kotlin, Android, Firebase Test Lab, Model View Presenter (MVP), APIs, Mobile Development, REST, Mobile App Development
Full-stack Android Developer
2019 - 2019
Johnson Lab & Supply (via Toptal)
- Created an Android app that allows field workers to log their work and upload photos and record their exact GPS location.
- Created an admin panel within the app that requires authentication and authorization. It allows the manager to manage projects and employees and export all collected data to be viewable on the PC.
- Designed a Firebase database and optimized it for bandwidth usage while keeping the data structure as flat as possible.
- Introduced the Firestore storage service to allow users to upload files that are referenced in the database and allow for assigning files to certain work items.
- Introduced Firebase Authentication to allow managers to authenticate when logging into the admin panel.
Technologies: Cloud Firestore, Mobile, Android SDK, GPS, Firebase Authentication, Firebase Realtime Database, Firebase, Kotlin, Android, REST APIs, Test-driven Development (TDD), Model View Presenter (MVP), Clean Architecture, APIs, Mobile Development, Mobile App Development, Mobile Architecture
Senior Android Developer
2017 - 2018
Disney Streaming Services
- Helped build an Android SDK for core functionalities within client apps in an organization, such as authentication, media streaming, and HTTP API communication layer.
- Maintained and improved Gradle quality plugins related to unit testing and code coverage.
- Improved the architecture of the SDK to improve testability and mocking for client apps.
Technologies: Mobile, Android SDK, Android Testing, Kotlin, Android, REST APIs, Model View Presenter (MVP), APIs, Mobile Development, REST, Retrofit, Mobile App Development, Mobile Architecture
Android Engineer
2017 - 2018
Max2 (via Toptal)
- Maintained and added new features to an enterprise application for businesses, where venue owners can manage their premises, staff, and client relations.
- Took care of the continuous integration environment by making sure it was paired up with the code review process.
- Advised a client with Android-specific decisions about design.
Technologies: Mobile, Android SDK, Android Testing, Bluetooth, Kotlin, Java, Android, REST APIs, Test-driven Development (TDD), Model View Presenter (MVP), APIs, Google Maps API, Mobile Development, Retrofit, Mobile App Development
Senior Android Developer
2016 - 2017
Tooploox
- Introduced continuous integration and continuous delivery to the project.
- Helped junior developers understand clean architecture and clean code principles.
- Worked on an Android project for a media industry client from the US.
- Advised the client about possible solutions for their problems.
- Provided designs to the design team that adheredf to material design principles.
Technologies: Cloud Firestore, Mobile, Android SDK, Android Testing, Kotlin, Clean Architecture, Espresso, JUnit, Jira, Jenkins, Java, Android, Scrum, Test-driven Development (TDD), Model View Presenter (MVP), Clean Code, APIs, Google Maps API, Mobile Development, Retrofit, Scrum Master, Mobile App Development
Lead Android Developer
2016 - 2016
X8 Digital Studio
- Created an Android app for an enterprise client from the UK that helps with networking during different conferences and meetups.
- Maintained different smaller Android apps within the company.
- Introduced CI/CD for all the projects under maintenance.
- Worked closely and directly with the clients to identify their needs and suggest optimal solutions.
- Refactored apps to work with clean architecture and clean code principles.
- Incorporated clean code principles into new projects.
Technologies: Mobile, Android SDK, Android Testing, Espresso, CircleCI, Git, JUnit, Jenkins, Java, Android, Scrum, Model View Presenter (MVP), Clean Architecture, APIs, Mobile Development, REST, Retrofit, Mobile App Development
Senior Android Developer
2013 - 2016
Ceneo sp. z o.o.
- Led the Android development team, which consisted of three people.
- Designed the architecture and implemented an Android app for the biggest price comparison company in Poland.
- Introduced CI/CD with Atlassian's Bamboo and Jenkins.
- Wrote UI and unit and integration tests using JUnit and Espresso frameworks.
- Helped the product owner to identify user needs and plan new features.
- Guided and taught best practices to new Android developers.
- Worked on the architecture following a Model–view–presenter (MVP) pattern.
Technologies: Mobile, Android SDK, Android Testing, Jira, Espresso, JUnit, Bamboo, Jenkins, Java, Android, Objective-C, Model View Presenter (MVP), Clean Architecture, Clean Code, APIs, Google Maps API, Mobile Development, REST, Scrum Master, Mobile App Development
Experience
Flutter App: Asphaltgold
EASY PARTICIPATION IN RAFFLES
Through the Asphaltgold app, you can easily and quickly participate in raffles for the hottest sneakers from Nike, Adidas, New Balance, and many other brands.
NEVER MISS A THING
Set up push notifications individually to your desired raffles and be informed automatically and conveniently at the start.
SECURE AND WITHOUT RISK
We handle your payment information with the highest level of security. You're always in control of your participation and orders. You can choose between Apple Pay, PayPal, and credit card as your payment method.
HEAT FOR NEED
With the app, you also have the option to access our "Heat for Need" category. "Heat for Need" is our in-house charity project which utilizes sneaker hype for a good cause by offering in-demand sneaker models that are already out of stock at an attractive price and donating the difference to the original retail price to changing charities.
Through the Asphaltgold app, you can easily and quickly participate in raffles for the hottest sneakers from Nike, Adidas, New Balance, and many other brands.
NEVER MISS A THING
Set up push notifications individually to your desired raffles and be informed automatically and conveniently at the start.
SECURE AND WITHOUT RISK
We handle your payment information with the highest level of security. You're always in control of your participation and orders. You can choose between Apple Pay, PayPal, and credit card as your payment method.
HEAT FOR NEED
With the app, you also have the option to access our "Heat for Need" category. "Heat for Need" is our in-house charity project which utilizes sneaker hype for a good cause by offering in-demand sneaker models that are already out of stock at an attractive price and donating the difference to the original retail price to changing charities.
Library: RESTMock
https://github.com/andrzejchm/RESTMockA library featured in Android Weekly: androidweekly.net/issues/issue-203.
It includes an HTTP server for Android instrumentation tests, allowing for mocking out HTTP requests and responses in test in a convenient way
It includes an HTTP server for Android instrumentation tests, allowing for mocking out HTTP requests and responses in test in a convenient way
Android App: Dubsmash
An app with over 100 million downloads.
Make lip-sync and dance videos with your favorite music, quotes, and movies! Dubsmash has the world’s largest selection of sounds from your favorite songs, shows, and movies.
Make lip-sync and dance videos with your favorite music, quotes, and movies! Dubsmash has the world’s largest selection of sounds from your favorite songs, shows, and movies.
iOS App: Ease
Ease (formerly EaseCentral) is benefits and HR software offered through your company’s insurance broker. It allows the management of time offs and employee benefits as well as approve time-off requests for the manager roles
Android App: Ease
Ease (formerly EaseCentral) is benefits and HR software offered through your company’s insurance broker. It allows to manage time offs, employee benefits as well as approve time-off requests for the manager roles
Android App: Viking App Poland
https://play.google.com/store/apps/details?id=com.vikingco.vikingapp.polandViking App is the official app for Mobile Vikings mobile network users. It allows for mobile plan management, including recurring payments, checking available balances, buying roaming packages, inviting other users, etc.
Android App: Howdy Hub
An app that provides a place for users to join communities they care about, discover and connect with like-minded members, and receive relevant content. Howdy enables users to save time, create opportunities, and grow their network through meaningful connections.
Android App: Ceneo
A mobile application that enables users to shop from anywhere in the world—safely and conveniently. Ceneo provides access to price comparison, Buy Now options, and the best deals on millions of products.
Library: DroidMVP
https://github.com/andrzejchm/DroidMVPA small Android library to help developers incorporate MVP, passive view, and presentation model patterns in an Android app. This library was featured in Android Weekly: androidweekly.net/issues/issue-211
Article: Presentation Model and Passive View in MVP – The Android Way
An article I wrote describing the new approach to the presentation model and passive view concepts for the model-view-presenter pattern for Android apps. This article was featured in Android Weekly: androidweekly.net/issues/issue-211
Article: ITDD – Instrumentation TDD for Android Using RESTMock
An article I wrote describing the approach to instrumentation tests in Android as a tool to be used for the TDD approach in delivering new features. This article was featured in Android Weekly: androidweekly.net/issues/issue-203
Education
2009 - 2014
Master's Degree in Computer Science
Wroclaw Univeristy of Technology - Wroclaw, Poland
Certifications
SEPTEMBER 2017 - PRESENT
React Academy
Toptal, LLC
OCTOBER 2014 - PRESENT
Oracle Certified Associate, Java SE 7 Programmer
Oracle
SEPTEMBER 2014 - PRESENT
Professional Scrum Master I
Scrum.org
Skills
Libraries/APIs
Firebase Android SDK, Retrofit, RxJava, Picasso, REST APIs, Mixpanel Android API, Alamofire, Chai, Google Maps API, React
Tools
Jira, Android Studio, Crashlytics, Jenkins, CircleCI, Firebase Cloud Messaging (FCM), Bamboo, Fastlane, Xcode, Firebase Test Lab, Firebase Authentication, Gradle, Apache Maven, OneSignal, TeamCity, Mocha, Git, GitHub, Trello, Branch.io, IntelliJ IDEA
Languages
Kotlin, Java, Dart, Swift, GraphQL, TypeScript, Objective-C, Python
Frameworks
Flutter, Dagger 2, Android SDK, JUnit, Robolectric, Express.js, Espresso, Swinject, Tailwind CSS
Paradigms
Model View Presenter (MVP), Test-driven Development (TDD), Scrum, Clean Architecture, Mobile Development, REST, Clean Code
Platforms
Mobile, Firebase, Android, iOS, Mixpanel, MacOS
Storage
SQLite, NoSQL, Firebase Realtime Database, Cloud Firestore, PostgreSQL
Other
Android Testing, OkHttp, Scrum Master, EventBus, Firebase Cloud Functions, APIs, Architecture, Mobile Architecture, Mobile App Development, 3D Printing, 3D Print Design, ESP8266, ESP32, Social Media Apps, Full-stack, Bluetooth, Videos, Video Processing, Video & Audio Processing, GPS, Axios, Team Leadership, Technical Leadership, Leadership, CI/CD Pipelines, Mobile Apps
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