Kamil Jakubczak, Developer in Poznań, Poland
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Kamil Jakubczak

Verified Expert  in Engineering

React Native Developer

Poznań, Poland

Toptal member since September 18, 2017

Bio

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

Camel Riding Sports LLC
React Native, AWS SDK, AWS CLI, AWS Lambda, Serverless, Firebase, TypeScript...
Brandon Miles
React, Node.js, NestJS, TypeScript, SQL
Quick Check, Ltd.
Firebase, React, React Native, Sass, Git, TypeScript, JavaScript...

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

Full-time

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

2022 - PRESENT
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.
Technologies: React Native, AWS SDK, AWS CLI, AWS Lambda, Serverless, Firebase, TypeScript, IAP SDK, React Native IAP, SQL

Full-stack Developer

2024 - 2025
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.
Technologies: React, Node.js, NestJS, TypeScript, SQL

React and React Native Developer

2018 - 2022
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.
Technologies: Firebase, React, React Native, Sass, Git, TypeScript, JavaScript, Continuous Integration (CI), Continuous Delivery (CD), Redux, CSS, Push Notifications, Mobile Development, iOS, Android

React Native Developer

2019 - 2019
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.
Technologies: React Native, JavaScript, Git, Redux, TypeScript, Push Notifications, Mobile Development, iOS, Android

React Native Expert

2019 - 2019
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.
Technologies: React Native, JavaScript, Git, Redux, Mobile Development, iOS, Android

React Native Developer

2018 - 2018
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.
Technologies: Push Notifications, React Native, Git, Redux, Mobile Development, iOS, Android

React and React Native Developer

2017 - 2018
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.
Technologies: Firebase, React Native, React, Redux, Mobile Development, iOS, Android

React Native Developer

2017 - 2018
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.
Technologies: React Native, JavaScript, Git, Redux, Mobile Development, iOS, Android

Full-stack Developer

2016 - 2018
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.
Technologies: .NET Core, React Native, React, Git, Continuous Delivery (CD), Continuous Integration (CI), Sass, Node.js, TypeScript, JavaScript, Redux, CSS, C#, Mobile Development, iOS, Android

React Native Developer

2017 - 2017
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.
Technologies: React Native, Git, Redux, Mobile Development, iOS, Android

Full-stack Developer

2015 - 2016
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.
Technologies: Microsoft SQL Server, Git, JavaScript, MongoDB, React, Node.js, CSS, C#, SQL

.NET Developer

2013 - 2015
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.
Technologies: Git, Microsoft SQL Server, CSS, C#, SQL

Experience

Meta Wallet

Developed the Meta Wallet SDK—a fully configurable, client‑embeddable digital wallet solution that retrieves JSON configuration from AWS S3 to enable custom branding (fonts, themes) and support for multiple payment methods, including alternative digital wallets and traditional credit card processing.

Meta Restaurant App

Architected a white‑label React Native platform that enables turnkey client‑specific app creation and App Store submission within a single day—requiring zero developer intervention. Using a dynamic application key, the system automatically pulls JSON configuration, branding assets (icons, fonts), package metadata (bundle ID, version), and other resources to generate fully branded builds ready for distribution.

OIDC Client for React Native

Designed and implemented an OIDC client to enable one‑to‑one hybrid authentication workflows and single sign‑on across mobile and web platforms. By leveraging Chrome Custom Tabs (Android) and SafariViewController (iOS) instead of WebView, the solution maintained cookie persistence and adhered to enterprise security standards while reusing the company’s existing authentication service.

Komplett Mobil

Developed a cross‑platform React Native application for a leading eCommerce and mobile network client to manage subscriptions and bill payments on both iOS and Android. I integrated an OIDC authentication client using ServiceIdentity (.NET Core) to ensure secure, seamless user login and identity management across platforms.

Focus Pointe Global

Developed a cross‑platform React Native application for Focus Pointe Global on iOS and Android, enabling users to cast votes, complete surveys, and visualize results through an intuitive, polished UI built with NativeBase.

Facebook-like Application for Products

Developed a social shopping mobile app that enables users to catalog owned and desired products, share collections with peers, and solicit feedback. I designed and implemented gamification features like “trendsetter” leaderboards and social discovery mechanics to increase user engagement and foster community interaction.

Breathalyzer Application

Developed a cross‑platform React Native mobile application integrating a breathalyzer device for comprehensive sobriety monitoring. I implemented background activity detection (driving vs. walking), randomized and scheduled test prompts, SMS/push notifications, and automated safety checks—such as requiring photo verification when driving is detected—to ensure compliance and user accountability.

Toptal Academy Lecturer | React Native

Served as a React Native Lecturer at Toptal Academy, designing and delivering a comprehensive curriculum that guided new developers through end‑to‑end mobile app development—from project setup and architecture to App Store and Google Play deployment—covering Firebase integrations, styling best practices, performance optimization (including native thread usage), and technology comparisons (React Native vs Expo and alternative cross‑platform frameworks). I shared actionable insights, advanced tips, and best practices to equip students with industry‑ready skills.

CeraCare App

Developed a cross‑platform React Native application for care workers to streamline daily patient management by centralizing patient profiles, care tasks, and status updates. I enabled secure, real‑time visibility into patient well‑being for both caregivers and family members, improving communication, accountability, and overall care coordination.

Education

2014 - 2016

Master of Science Degree in Computer Science

Poznan University of Technology - Poznań, Poland

2010 - 2014

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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