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Leo Brdar
Verified Expert in Engineering
Full-stack Developer
Zagreb, Croatia
Toptal member since June 5, 2025
Bio
Leo is a full-stack developer with 10 years of experience delivering high-impact solutions to corporations and startups across healthtech, education, and nonprofits. Specializing in React, React Native, TypeScript, Redux, GraphQL, Apollo, and Node.js, he has architected enterprise SaaS platforms and built a job-matching portal that connected millions of African users to global tech roles. Leo effectively leads and mentors teams, manages and resolves conflicts, and ensures timely delivery.
Portfolio
Cobalt Hills Tech
Management, Entrepreneurship, Business Development, Communication...
ServiceNow
TypeScript, React, React Query, Zustand, Playwright, Cypress, Jest...
heyPatient
React, React Native, Next.js, TypeScript, Apollo, GraphQL, Tailwind CSS, GitHub...
Experience
- JavaScript - 10 years
- React - 10 years
- Redux - 9 years
- React Native - 8 years
- TypeScript - 7 years
- GraphQL - 6 years
- Node.js - 6 years
- Apollo - 5 years
Preferred Environment
MacOS, WebStorm, Chrome
The most amazing...
...thing I've built is a portal that automates job placements—transforming millions of lives across Africa by connecting them with global big tech opportunities.
Work Experience
CEO and Lead Software Engineer
2021 - PRESENT
Cobalt Hills Tech
- Negotiated and signed multiple successful international B2B contracts with clients across diverse industries.
- Managed a portfolio of software development projects, delivering value to clients through developing, managing, consulting, and educating.
- Adapted to fluctuating market demands by diversifying services, increasing client satisfaction, and achieving revenue stability across multiple industries.
- Secured long-term partnerships, contributing to consistent revenue streams over the past four years.
Technologies: Management, Entrepreneurship, Business Development, Communication, People Management, Interpersonal Skills
Senior Software Engineer
2025 - 2026
ServiceNow
- Operated within a rapidly scaling security startup environment that was later integrated into a large enterprise ecosystem.
- Led the development of a company-wide design system, ensuring WCAG-compliant accessibility and scalable UI standards across product teams.
- Established structured product feedback loops by integrating PostHog analytics and in-app surveys, enabling data-driven roadmap decisions.
- Increased engineering quality by expanding unit and end-to-end testing strategy to 90% coverage across critical modules.
- Contributed to core features of an enterprise-grade identity and access intelligence SaaS platform used by security-focused organizations.
Technologies: TypeScript, React, React Query, Zustand, Playwright, Cypress, Jest, GitHub Actions, Ark UI, Web Content Accessibility Guidelines (WCAG)
Lead Software Engineer
2023 - 2025
heyPatient
- Led the development of a SaaS healthtech system supporting 10+ hospitals and serving over 60,000 patients.
- Developed a white-labeled mobile application along with 12 fully branded versions for iOS and Android, ensuring seamless user experience across multiple hospitals.
- Integrated proprietary in-house navigation SDKs by building native bridges and enhancing functionality and user engagement.
- Simplified deployments and saved time by introducing CI/CD pipelines using GitHub Actions and Azure Pipelines.
- Ensured the team delivered quality code by fostering a strong culture of collaboration and thorough code reviews.
- Showcased features to stakeholders through demonstrations, making the system's value and capabilities clear.
- Developed a real-time queueing system using GraphQL subscriptions over WebSockets, enabling instant updates and improved operational efficiency.
Technologies: React, React Native, Next.js, TypeScript, Apollo, GraphQL, Tailwind CSS, GitHub, GitHub Actions, Pipelines, MacOS, WebStorm, Chrome, Software Engineering, Jira
Lead Software Engineer & Manager
2021 - 2023
African Leadership Group
- Developed a platform that automates job placements, transforming the lives of millions of users across Africa by connecting them with opportunities in big tech.
- Managed an international cross-functional team of six, ensuring alignment with project and product managers to deliver impactful products on time.
- Handled hiring and recruitment to onboard talented developers who fit well with the team culture.
- Ran sprint ceremonies and retrospectives to keep the team aligned and motivated.
- Built integrations with multiple services, including Sovren, SendGrid, and DocuSign, to enhance platform capabilities and streamline business workflows.
Technologies: React, TypeScript, Apollo, Redux, GraphQL, Nexus, Prisma, Tailwind CSS, Webpack, GitHub, Amazon Cognito, Amazon S3 (AWS S3), Ant Design, Stripe API, PostgreSQL, MongoDB, MacOS, WebStorm, Chrome, Software Engineering, Jira
Lead Software Engineer
2019 - 2021
Rosetta Stone
- Mentored senior engineers, leveraging expertise and experience to smooth their transition from one tech stack to another.
- Led knowledge-sharing workshops, reviewed designs, and managed budgets for training and team-building activities.
- Ensured application stability and quality through test-driven development (TDD) and achieved 100% code coverage, reinforcing robust and reliable software delivery.
- Drove the development of a cross-platform application tailored for children in schools. Integrated speech recognition, 3D engine libraries, and a headless CMS and optimized memory and performance.
- Architected and developed a monorepo to house features shared across all products. Contributed to multiple packages, fostering discussions on code conventions, architecture, and best practices to enhance the overall efficiency of five applications.
Technologies: ReactXP, React Native, React, TypeScript, Apollo, GraphQL, Redux, Emotion, Storybook, RxJS, Git, Speech Recognition, 3D Graphics Engines, Jest, Nightwatch.js, Contentful, MacOS, WebStorm, Chrome, Software Engineering, Jira
React Consultant
2017 - 2020
E-Glas
- Led and mentored engineers, guiding them on best practices through comprehensive code reviews.
- Contributed across the full software development lifecycle, from requirements gathering and application design to mentoring developers through implementation, testing, and maintenance phases.
- Conducted knowledge-sharing workshops to train junior engineers and enhance their skills.
Technologies: JavaScript, React, Node.js, Redux, Git, MySQL, Babel, Webpack, Knex.js, Trello, MacOS, WebStorm, Chrome, Software Engineering, GitHub
JavaScript Engineer
2018 - 2019
Infinum
- Organized and served as a speaker at the Infinum JS Talks meetup, contributing to the knowledge-sharing and growth of the local tech community.
- Mentored junior engineers and summer interns, fostering their technical skills and professional development.
- Collaborated within an international team, guiding the development process and conducting thorough code reviews to ensure high-quality deliverables.
Technologies: JavaScript, TypeScript, React, Next.js, Node.js, MobX, Emotion, Storybook, Babel, Webpack, Git, MySQL, TSLint, MacOS, WebStorm, Chrome, Software Engineering, GitHub
Full-stack JavaScript Developer
2016 - 2018
Dickey's Barbecue Pit
- Developed four applications for online ordering and back-office restaurants' administration.
- Built and implemented the Stripe API integration, enabling seamless payment processing online and via in-store POS systems.
- Served as the mobile team lead, guiding development efforts, ensuring timely delivery of key deliverables, and orchestrating 1-on-1 sessions with team members.
- Interfaced effectively with clients to understand requirements and ensure project success.
Technologies: JavaScript, Node.js, React, React Native, GraphQL, Relay, Redux, Webpack, Babel, ESLint, Jira, Bitbucket, MacOS, WebStorm, Chrome, Software Engineering, Stripe API, Amazon S3 (AWS S3), Amazon Cognito, GitHub
Experience
Lexia English Language Development
https://www.lexialearning.com/lexia-english/A cross-platform application tailored for children in schools learning English as a second language.
The app works across web, iOS, and Android platforms and provides a very engaging video game experience to appeal to children. It uses a 3D engine, a speech recognition engine, and rich content pulled from the Contentful API. The app also supports adaptive learning, dynamically calculating the next level and pulling appropriate content based on user scores.
The app works across web, iOS, and Android platforms and provides a very engaging video game experience to appeal to children. It uses a 3D engine, a speech recognition engine, and rich content pulled from the Contentful API. The app also supports adaptive learning, dynamically calculating the next level and pulling appropriate content based on user scores.
Member Portal
A web platform for semi-automated matching of African talent with global opportunities to make an impact with their expertise.
This member portal results from the African Leadership Group's commitment to finding, developing, and connecting high-performing talent to the world's leading employers over the past 17 years.
This member portal results from the African Leadership Group's commitment to finding, developing, and connecting high-performing talent to the world's leading employers over the past 17 years.
Education
2016 - 2018
Master's Degree in Software Engineering
Faculty of Engineering, University of Rijeka - Rijeka, Croatia
Skills
Libraries/APIs
React, Node.js, MobX, Emotion, ReactXP, RxJS, Nightwatch.js, Stripe API, GraphQL API, SendGrid API, React Query, Playwright, Ark UI
Tools
Webpack, WebStorm, Babel, Jira, Bitbucket, Git, Knex.js, Trello, Prisma, GitHub, Amazon Cognito
Languages
JavaScript, GraphQL, TypeScript
Frameworks
React Native, Redux, Tailwind CSS, Chrome, Relay, Next.js, Jest, Ant Design, Cypress
Paradigms
Management
Platforms
MacOS, Contentful, Nexus
Storage
MySQL, Amazon S3 (AWS S3), PostgreSQL, MongoDB
Other
Apollo, Software Engineering, Algorithms, Data Structures, Machine Learning, Artificial Intelligence (AI), Human-machine Interface (HMI), Web3, ESLint, Storybook, TSLint, Speech Recognition, 3D Graphics Engines, GitHub Actions, Pipelines, DocuSign, Entrepreneurship, Business Development, Communication, People Management, Interpersonal Skills, Zustand, Web Content Accessibility Guidelines (WCAG)
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