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Alex Crookes
Verified Expert in Engineering
Mobile Engineer and Developer
Oakville, ON, Canada
Toptal member since April 7, 2026
Bio
Alex is a mobile engineer with 15+ years of experience building Android apps using Kotlin and Java, iOS, and React Native, with a focus on keeping platforms in sync to improve delivery. He modernizes legacy codebases using a tidy-first approach to reduce risk while delivering new value. Alex engages deeply with process and communication, helping teams plan clearly, unblock quickly, and ship with steady velocity.
Portfolio
Havas CX
Kotlin, Android, REST, Jetpack Compose, Model View Intent (MVI)...
Alchemist One
Swift, iOS, Android, Kotlin, Jetpack Compose, Room
Stan
React Native, REST, Product Management, Lean Product Development
Experience
- Team Building - 20 years
- Problem Solving - 20 years
- Refactoring - 15 years
- Android - 15 years
- Software Architecture - 15 years
- Kotlin - 10 years
- Model View Intent (MVI) - 5 years
- Jetpack Compose - 5 years
Preferred Environment
Android, iOS, React Native, TypeScript, Kotlin, Kotlin Multiplatform Mobile (KMM)
The most amazing...
...app I've been involved in featured real-time location tracking and software crash detection years ahead of competitors, setting a new standard in innovation.
Work Experience
Mobile Lead
2025 - 2026
Havas CX
- Refactored legacy MVP/XML Android code into modern MVVM/MVI with Compose using dependency inversion, increasing test coverage from 0% to over 45% and reducing LOC by approximately 30%.
- Standardized Compose patterns and state/event flow, moving the app from inconsistent Compose usage to a cohesive, maintainable approach across the project.
- Replaced legacy SAML authentication by migrating to OAuth2 using Auth0 by Okta with custom tabs. Implemented partner-specific SSO redirect and handler flows, resulting in zero mobile findings from a third-party pen test in Jul 2025.
- Introduced a lightweight caching module for the network layer, keeping the UI responsive while caching ran asynchronously. Improved cold start to main screen from approximately 5s to around 0.5s, according to internal estimates.
- Re-architected the BFF/server-driven UI into template-based components with theming and variants, making partner changes safer and reducing the need for bespoke UI components.
- Doubled team velocity through improved coding standards, PRs, unit tests, and pre-coding alignment.
- Established practical LLM-assisted development workflows and guidelines to accelerate delivery while maintaining reviews and tests as guardrails.
Technologies: Kotlin, Android, REST, Jetpack Compose, Model View Intent (MVI), Model View ViewModel (MVVM)
Mobile Lead
2024 - 2024
Alchemist One
- Ported an iOS MVC app to Android using Kotlin, Compose, and MVI in 5 weeks, collaborating directly with the CEO, CTO, product, design, and users.
- Achieved over 80% automated test coverage and documented patterns/tests to ensure a smooth handoff.
- Created guidelines for the iOS development team to refactor the iOS/Swift app, resolving architectural issues and improving performance.
Technologies: Swift, iOS, Android, Kotlin, Jetpack Compose, Room
Mobile Lead Engineer (Contract)
2024 - 2024
Stan
- Refactored a broken React Native POC into a shippable app by introducing TypeScript, predictable state management, and clear layering.
- Upgraded React Native from 0.63 to 0.74 and shipped the app to both Play and App Store in 11 weeks.
- Conducted multiple customer interviews to guide each project revision, achieving a 61% "Sean Ellis" score.
- Demonstrated that the company could achieve more by realigning the web platform to use React Native code, eliminating the need for a mobile app.
Technologies: React Native, REST, Product Management, Lean Product Development
Principal Android Developer
2022 - 2023
ASICS | Runkeeper
- Fixed location-tracking architecture issues that were driving crashes and power drain. Improved crash-free users to 99.99% and battery life by 20%+.
- Modularized a monolithic Java app into approximately 12 reusable and testable modules. Extracted shared platform modules for the design system, networking, caching, and location, reducing the codebase by about 28%.
- Made unit tests a shipping default and wired them into CI checks to improve delivery confidence and code quality. Increased automated test coverage from 8% to 70%.
- Drove a cross-platform design system effort across Android, iOS, Figma, and documentation, reducing UI duplication and improving consistency, resulting in an estimated 40% reduction in UI code.
- Improved onboarding by 24% and engagement by 18% by architecting and delivering key initiatives like "My First Steps" and "Creators," aligning implementation across teams.
Technologies: Kotlin, Model View ViewModel (MVVM), React Native, Geolocation, Refactoring, Code Refactoring
Architect, Engineering Manager, and Mobile Lead
2008 - 2022
EatSleepRIDE
- Built a platform supporting over 10,000 concurrent motorcyclists, with core background location and telemetry tracking optimized for accuracy, performance, and battery usage.
- Designed and shipped a software-only crash detection capability on Android and iOS (2009) for safety-critical scenarios.
- Built and ran the teams that shipped all levels of software.
- Built a gamification platform that increased usage by over 300%, later licensed by Harley Davidson and other OEMs.
- Implemented machine learning with on-device edge models to detect riding and derive a safety score from telematics, enabling new fintech market products.
- Shipped Apple Watch, Wear operating system, Apple CarPlay, and motorcycle head unit integration via MySpin, introducing CI and quality gates for high reliability through ongoing architecture work.
Technologies: Kotlin, Android, Swift, Android NDK, Android SDK, Jetpack Compose, Realm, NoSQL, JavaScript, Java, MySQL, PostgreSQL, Redis, Node.js, Express.js, React Native, React
Experience
Scope Tickets
https://www.scopetickets.comA web and mobile platform allowing event organizers a full suite of ticketing and promotion activities.
I worked with Scope to port the original PoC code to a fully-realized Android app using Kotlin/Compose, most of which required a "tidy first" refactoring approach. I introduced an SWR pattern for managing admissions that ensured that clients synchronized ticket usage more reliably and even tolerated offline usage.
I worked with Scope to port the original PoC code to a fully-realized Android app using Kotlin/Compose, most of which required a "tidy first" refactoring approach. I introduced an SWR pattern for managing admissions that ensured that clients synchronized ticket usage more reliably and even tolerated offline usage.
A Unified Design System for ASICS/Runkeeper
https://play.google.com/store/search?q=Runkeeper&c=appsRunkeeper is an ASICS-owned app that helps improve their running and fitness. The company consisted of multiple "feature" pods, each with its own designers and developers, resulting in a disjointed UI.
I worked to organize the developer leads to adopt a unified design system based on Compose/SwiftUI. The key deliverable was less the code than the system itself. It comprised not only versioned and reusable modules for iOS, Android, and the web, but also the same elements in a Figma library. Success was further achieved through a focus on clear naming and utility for each component, which linked the code to a Figma library and a demo app for each platform, so designers could see how things were implemented and explore them. This reduced UI code by around 40% and significantly increased delivery velocity.
I worked to organize the developer leads to adopt a unified design system based on Compose/SwiftUI. The key deliverable was less the code than the system itself. It comprised not only versioned and reusable modules for iOS, Android, and the web, but also the same elements in a Figma library. Success was further achieved through a focus on clear naming and utility for each component, which linked the code to a Figma library and a demo app for each platform, so designers could see how things were implemented and explore them. This reduced UI code by around 40% and significantly increased delivery velocity.
Software-based Crash Detection for Motorcycles | EatSleepRIDE
EatSleepRIDE is a geo-tracking app for motorcyclists. After developing a theory that the sensors were "good enough to track a crash" back in 2008, I built a platform to capture telematics data from motorcycle riding. We then used this with experimental protocols from "throwing sandbags off of a truck" to robotics (in conjunction with a local college) to build a model that could track crashes in real time and solely on the device.
After delivering this in 2009 and receiving feedback that it had saved lives, it was ported to Android and continuously refined. In 2016, it was revamped using machine learning and led to 2 further models:
• Discrete identification of motorcycle riding (distinct from other vehicles).
• A "Safe Riding" protocol that was later developed as a product for motorcycle insurance companies.
After delivering this in 2009 and receiving feedback that it had saved lives, it was ported to Android and continuously refined. In 2016, it was revamped using machine learning and led to 2 further models:
• Discrete identification of motorcycle riding (distinct from other vehicles).
• A "Safe Riding" protocol that was later developed as a product for motorcycle insurance companies.
Education
1992 - 1993
Master's Degree in Water Pollution Control Technology
Cranfield University - Cranfield, United Kingdom
1989 - 1992
Bachelor's Degree in Mechanical Engineering
University of Manchester - Manchester, United Kingdom
Skills
Libraries/APIs
Node.js, React
Tools
Android NDK, Figma
Languages
Kotlin, TypeScript, Swift, JavaScript, Java
Paradigms
REST, Model View Intent (MVI), Model View ViewModel (MVVM), Refactoring, Code Refactoring
Platforms
Android, iOS
Frameworks
React Native, Android SDK, Express.js, SwiftUI
Storage
Realm, NoSQL, MySQL, PostgreSQL, Redis
Other
Problem Solving, Critical Thinking, Jetpack Compose, Geolocation, Team Building, Kotlin Multiplatform Mobile (KMM), Software Architecture, IT Project Management, Environmental Engineering, Projects, Product Management, Lean Product Development, Room, Patterns, Telematics, Sensor Fusion
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