
Kamil Jakubczak
Verified Expert in Engineering
React Native Developer
Poznań, Poland
Toptal member since September 18, 2017
Kamil is a full‑stack engineer specializing in React, React Native, and TypeScript. He has a proven ability to architect scalable applications, build robust CI/CD pipelines, and deliver end‑to‑end solutions—from enterprise platforms to startup products and solo projects. Kamil is skilled at taking concepts from ideation to production on both cloud and mobile, writing clean, maintainable code, and optimizing performance.
Portfolio
Experience
- JavaScript - 12 years
- React - 10 years
- Node.js - 10 years
- React Native - 9 years
- TypeScript - 9 years
- Continuous Integration (CI) - 5 years
- AWS Lambda - 4 years
- AWS SDK - 4 years
Availability
Preferred Environment
WebStorm, Cursor AI, MacOS, DataGrip
The most amazing...
...project I've worked on was Norway’s largest eCommerce platform, serving millions of daily visits with scalable React Native and back-end solutions.
Work Experience
Mobile React Native Developer
Camel Riding Sports LLC
- Architected and built a React Native mobile application from the ground up, owning the entire front-end development lifecycle from design through production release.
- Assumed full back-end ownership after a team transition, refactoring and stabilizing services to deliver reliable, end‑to‑end functionality.
- Collaborated with stakeholders to evaluate and select optimal third‑party tools, APIs, and data services, ensuring alignment with product requirements and scalability goals.
- Designed and implemented a scalable AWS infrastructure—leveraging AWS Lambda, API Gateway, Amazon RDS (MySQL) with RDS Proxy, and S3—to support robust back-end services, secure data storage, and streamlined CI/CD deployment pipelines.
- Provided continuous application maintenance and support from day one, proactively monitoring performance, resolving issues, and deploying updates.
- Guided the client through App Store submission processes, optimizing build configurations to comply with platform standards and accelerate time to market.
- Advised product owners on feature prioritization, UX considerations, and compliance guidelines to ensure new functionality met user needs and regulatory requirements.
- Organized and delegated development tasks, mentored junior engineers, and established best practices to maintain code quality and team productivity.
- Developed a strategic roadmap of future enhancements, delivering actionable recommendations to evolve the product and improve user engagement.
- Designed and integrated a subscription‑based monetization model using native in‑app purchase frameworks (Apple App Store and Google Play Billing), enabling seamless recurring payments and streamlined checkout experiences.
Full-stack Developer
Brandon Miles
- Conducted a comprehensive technical audit of the existing application, identifying critical defects, performance bottlenecks, and architectural shortcomings.
- Developed a prioritized remediation roadmap and implementation plan to address legacy issues and enhance maintainability.
- Implemented high‑impact fixes to stabilize production, resolving key bugs and optimizing performance across core workflows.
- Initiated and architected a new front-end prototype to modernize the codebase, improve scalability, and streamline future feature development.
- Built a lightweight back-end proof‑of‑concept to validate demo scenarios and support integration testing.
- Advised leadership on optimal technology choices, architectural patterns, and tooling to align the product with industry best practices.
- Orchestrated a seamless handoff of the application to an external development team by producing detailed documentation, conducting technical onboarding sessions, and ensuring continuity of knowledge.
React and React Native Developer
Quick Check, Ltd.
- Led a full‑scale refactor of the company’s flagship mobile app to resolve performance bottlenecks and improve stability.
- Architected and delivered core features, including Google Maps integration, Apple Pay/Google Pay support, location‑based search, and NFC‑based hotel room access, to expand platform functionality.
- Consolidated separate iOS (Objective‑C) and Android (Java) wallet apps into a unified React Native codebase, reducing maintenance overhead and accelerating feature delivery.
- Developed a cross‑platform wallet SDK (React Native for Web) for external clients, enabling turnkey integration into third‑party web applications without additional engineering resources.
- Engineered native door‑unlocking libraries with React Native bindings to support secure, contactless hotel check‑in workflows.
- Established automated CI/CD pipelines with Bitbucket Pipelines and Microsoft App Center, replacing manual builds with on‑demand releases and significantly reducing build time.
- Built scalable tooling and configuration frameworks to auto‑generate client‑specific mobile apps, eliminating developer involvement for new deployments.
- Managed end‑to‑end deployment processes for iOS, Android, and web projects, overseeing App Store, Google Play, and Bitbucket Pipelines releases with a consistent success rate.
React Native Developer
Scholly, Inc.
- Upgraded the React Native codebase from a legacy version to the latest stable release, ensuring compatibility with modern APIs and improving overall app maintainability.
- Designed and implemented an interactive image‑cropping component for camera captures, enabling users to easily select and submit precise regions for analysis.
- Optimized performance on resource‑intensive screens—particularly the camera view—eliminating frame tearing at startup and enhancing rendering smoothness.
- Refined the image‑processing pipeline and built intuitive result‑display screens, ensuring accurate analysis outputs and a seamless user experience.
React Native Expert
Monarch Money
- Upgraded the React Native codebase from version 0.59 to 0.60.x, ensuring compatibility with the latest platform APIs and improving long‑term maintainability.
- Implemented Microsoft CodePush for seamless over‑the‑air updates, enabling rapid distribution of bug fixes and feature enhancements without requiring full App Store releases.
- Corrected source map generation in the build pipeline and integrated proper Sentry uploads to enable precise error tracking and accelerated debugging.
- Diagnosed and resolved a critical Android build failure, restoring full CI/CD build functionality and preventing release delays.
- Conducted a comprehensive codebase audit to identify potential stability and performance risks, producing actionable recommendations to proactively mitigate future issues.
React Native Developer
Golden Era Club, Ltd.
- Spearheaded end‑to‑end development of a cross‑platform mobile application—from initial concept sketches through architecture, development, testing, and production deployment—delivering a fully standalone product.
- Defined and implemented scalable data models, API mapping strategies, and updated workflows to simplify integration with existing services and support future feature iterations.
- Architected and launched an Expo‑based CI/CD pipeline, automating builds, testing, and over‑the‑air releases to accelerate delivery cycles and ensure consistent quality across iOS and Android.
- Collaborated closely with design, product, and engineering stakeholders to drive UI/UX decisions, prioritize features, and align development efforts with business goals.
React and React Native Developer
Brand Method
- Developed and deployed Firebase Cloud Functions to power core back-end features—including breath analysis and facial recognition—enabling secure, server‑side biometric processing.
- Engineered background task orchestration in React Native to monitor user activity (walking vs. driving) and trigger context‑aware testing workflows on demand.
- Implemented a cron‑based scheduling system with Firebase Cloud Functions to automate periodic data collection, processing, and user notifications.
- Integrated a native breath analyzer SDK into the React Native app via custom bindings, facilitating in‑app biometric measurement with minimal latency.
- Integrated a facial recognition API to enforce user identity verification, ensuring compliance with legal requirements and safeguarding against unauthorized access.
React Native Developer
Suits & Sandals
- Identified and resolved critical pre‑release stability and performance issues in a React Native application, integrating Firebase Crashlytics, Analytics, and Performance Monitoring to enhance observability and reduce error rates.
- Conducted comprehensive code reviews and profiling to eliminate bottlenecks, documenting potential technical risks and prescribing mitigation strategies for upcoming feature development.
- Optimized polling and authentication workflows by refactoring inefficient logic and streamlining state management, improving load times and delivering a smoother user experience.
Full-stack Developer
Fabres
- Led the evaluation and adoption of emerging front‑end technologies across new initiatives and legacy projects, driving standardization and improving developer productivity.
- Architected and delivered multiple applications from proof‑of‑concept through production, selecting optimal front‑end frameworks and tooling to align with product roadmaps and scalability needs.
- Designed and implemented robust CI/CD pipelines for .NET Core services, enabling streamlined deployments and accelerating release cadence across the engineering organization.
- Translated complex client requirements into scalable technical solutions, maintaining and enhancing several high‑traffic production applications.
- Developed the company’s inaugural React Native mobile application—establishing a new customer‑facing channel that received strong user adoption and positive feedback.
- Built end‑to‑end CI/CD workflows for mobile development from scratch, automating build, test, and release processes to improve delivery speed and reliability.
- Mentored cross‑functional engineering teams on front‑end architecture, performance optimization, and troubleshooting, fostering a culture of continuous improvement and code quality.
React Native Developer
Dry Good Technology, LLC
- Refactored and optimized a large‑scale React Native application, migrating state management to Redux to resolve performance bottlenecks and enhance maintainability.
- Designed and implemented advanced UI animations—including shared element transitions—to deliver smooth, visually engaging user experiences.
- Conducted extensive codebase refactoring to improve modularity, reduce technical debt, and streamline component architecture.
- Provided ongoing technical consultancy to client stakeholders, defining best practices and scalable solutions for complex React Native feature development and future enhancements.
Full-stack Developer
Sputnik Software
- Developed a React‑based web application for a government grant portal, replacing a legacy Knockout.js implementation and establishing React as the company’s standard front‑end framework.
- Initiated the design of a microservice‑driven architecture using Docker and Node.js, laying the foundation for scalable, decoupled service deployments.
- Architected and delivered a centralized identity microservice (Node.js + OrientDB) to provide unified authentication and user management across multiple systems.
- Built a client‑facing CMS with a Node.js back end and React front end, modernizing content workflows and demonstrating a proof‑of‑concept for future platform enhancements.
- Led an R&D engineering team, translating complex government requirements into technical specifications and guiding end‑to‑end solution development.
- Designed a data‑synchronization solution for two major government agencies, enabling secure sharing and real‑time consistency of customer records across separate systems.
.NET Developer
Sputnik Software
- Supported a large‑scale, citizen‑facing government platform comprised of multiple applications for applying to cultural projects, heritage renovation, and event funding programs.
- Maintained and modernized a legacy codebase while concurrently designing and delivering new features to enhance platform functionality.
- Partnered directly with government stakeholders to present proposed solutions, gather feedback, and ensure alignment with evolving requirements.
- Championed the adoption of modern development tools and best practices among senior engineers, fostering cross‑functional knowledge sharing and technical growth.
- Designed and implemented over 50 dynamic form workflows for annual cultural event grant submissions, streamlining the application process and improving user experience.
Experience
Meta Wallet
Meta Restaurant App
OIDC Client for React Native
Komplett Mobil
Focus Pointe Global
Facebook-like Application for Products
Breathalyzer Application
Toptal Academy Lecturer | React Native
CeraCare App
Education
Master of Science Degree in Computer Science
Poznan University of Technology - Poznań, Poland
Bachelor of Science Degree in Computer Science
Poznan University of Technology - Poznań, Poland
Skills
Libraries/APIs
React, Node.js
Tools
WebStorm, AWS SDK, Git, AWS CLI, DataGrip
Languages
SQL, JavaScript, TypeScript, CSS, C#, Sass
Frameworks
React Native, Redux, .NET Core, NestJS
Paradigms
Mobile Development, Continuous Integration (CI), Continuous Delivery (CD)
Platforms
Firebase, AWS Lambda, iOS, Android, MacOS
Storage
Microsoft SQL Server, MongoDB
Other
Push Notifications, Serverless, IAP SDK, React Native IAP, Cursor AI
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