Build React & Next.js applications
From greenfield products to complex multi-app platforms with shared architecture and consistent patterns.
Nikola Kikanovic
Senior Frontend Engineer
Building scalable React & Next.js applications for high-traffic platforms and enterprise teams.
ReactNext.jsTypeScriptFrontend ArchitectureTestingStorybook
01.
About Me
Senior frontend engineer with 6+ years shipping production applications for iGaming, FinTech, and enterprise teams.
I'm a senior frontend engineer based in Belgrade with 6+ years building production applications for iGaming, FinTech, eCommerce, and enterprise teams.
My work centers on what teams actually need at scale: React and Next.js architecture, legacy migrations, shared component systems, testing practices, and delivery workflows that keep code maintainable as products grow.
I've led frontend modernization across multiple apps, built shared Storybook modules and auth layers, shipped real-time interfaces for high-traffic platforms, and helped teams adopt TypeScript, better reviews, and AI-assisted development.
02.
Tech Stack
React
Next.js
Node.js
PHP
TypeScript
JavaScript
TailwindCSS
Storybook
MySQL
MariaDB
Docker
ArgoCD
GitLab
AWS
Azure
Yarn
Apollo
Claude Code
Cursor
03.
How I Can Help
I work with teams that need scalable React and Next.js applications — not just pages, but architecture that lasts.
Modernize legacy frontends
Migrate jQuery, Backbone, and vanilla JS codebases to React and TypeScript without disrupting production.
Design scalable frontend architecture
Reusable component libraries, Storybook workflows, auth modules, and state management that teams can maintain.
Improve performance & quality
Code reviews, testing practices, SonarQube analysis, and delivery optimizations that reduce regressions.
Help teams level up
Mentoring, knowledge sharing, and adopting TypeScript, testing, and AI-assisted development workflows.
04.
Selected Work
Real production challenges — anonymized where needed — with the approach taken and impact delivered.
iGaming · Real-time interfaces
Scalable frontend for a multi-brand gaming platform
- Challenge
- Multiple live casino brands needed reliable betting interfaces, streaming modules, and consistent UX under high traffic.
- Solution
- Built and maintained real-time interfaces across brands, led Backbone-to-Preact migration, and implemented video streaming and communication modules.
- Impact
- Delivered stable live betting experiences across platforms and mentored a growing frontend team.
- React
- Real-time UX
- Migration
- Mentoring
FinTech · Multi-app ecosystem
Shared frontend platform for enterprise applications
- Challenge
- Several frontend applications duplicated components, auth logic, and patterns — slowing delivery and increasing bugs.
- Solution
- Introduced a shared Storybook component module, centralized next-auth with Keycloak, adopted Zustand, and established Vitest testing practices.
- Impact
- More maintainable codebases, faster feature delivery, and stronger code quality through reviews and SonarQube.
- Next.js
- TypeScript
- Storybook
- Testing
Enterprise · Platform modernization
Legacy-to-React migration across production apps
- Challenge
- Five or more production applications still ran on jQuery and vanilla JavaScript with inconsistent practices and slow iteration.
- Solution
- Architected React and TypeScript structure, introduced code reviews and testing, and integrated AI-assisted workflows for generation and review.
- Impact
- Reduced development cycle time by around 30% and established modern frontend standards across the team.
- React
- TypeScript
- Architecture
- AI Workflow
05.
Where I've Worked
A timeline of roles where I shipped products, improved architecture, and helped teams level up.
Senior Software Engineer @ Gemini Infotech
Jul 2024 – Present- Architected codebase structure with good practices and introduced code reviews and testing practices in a team.
- Actively developing and maintaining custom CMS.
- Developing casino platform features with an AI-assisted workflow using Claude and Cursor.
- Reduced development cycle time around 30% by leveraging LLM tooling for code generation and review.
- Maintained interactive user interfaces using PHP, jQuery, and JavaScript.
- Led team in adopting TypeScript & React best practices.
- Implemented SEO best practices to improve organic search rankings.
- Refactored 5+ apps from jQuery, JavaScript to React & TypeScript.
Founder @ Sanis Tech
Jul 2024 – Present- Led the development of high-performance web and eCommerce platforms across diverse industries including retail, real estate, education, and big data.
- Delivered enterprise-level solutions for clients such as Walmart and Axpo, ensuring scalability, security, and seamless user experience.
- Built and maintained Next.js-based applications with technologies like React, TailwindCSS, SASS, Docker, and PHP.
- Collaborated on data-driven platforms integrating PowerBI, Azure, AWS, and MariaDB for analytics and reporting.
- Created custom learning and real estate platforms with responsive UI/UX, optimized performance, and modular component architecture.
- Contributed to the design and implementation of admin dashboards, eCommerce systems, and big data tools using modern frontend frameworks.
Software Engineer @ Bakson Ltd
May 2022 – Jul 2024- Developing application with role/permission management tool for management and client facing needs with Next.js and TypeScript.
- Implemented and maintained components module for all frontend applications with Storybook.
- Implemented and maintained next-auth module for all FE apps, which work with Keycloak.
- Improvement of code review processes, and the dissemination of knowledge through presentations on new and interesting technologies.
- Made code more readable and maintainable by introducing Zustand state management library to other projects.
- Leveraging SonarQube in the software development process to conduct code quality analysis, identify bugs, security vulnerabilities, and code smells, and provide actionable insights for improving software maintainability and reliability.
- Actively engaged in writing unit and integration tests as part of ongoing software development, utilizing mocking frameworks (e.g., Vitest) for unit tests to isolate components and integration tests (Apollo's MockedProvider) to verify seamless interactions between modules, ensuring the robustness and reliability of software applications.
- Work with Docker containers, ArgoCD and Gitlab.
Frontend Developer - iGaming (Dafabet, Nextbet) @ Sportion
Mar 2020 – May 2022- Built real-time betting interfaces serving live users across Dafabet and Nextbet platforms.
- Migrate project from Backbone.js to Preact.
- Led the implementation of video streaming and communication modules ensuring seamless interaction between betters and application.
- Experience in web-applications development based on MVC (Model-View-Control frameworks) using Backbone.JS and CoffeeScript.
- Refactor and maintain code in Backbone.js for web application.
- Mentoring a small team of 2 juniors and 1 mediator.
06.
What Colleagues Say
Feedback from teams I have worked with on architecture, migrations, and production delivery.
Nikola brought structure to our frontend when we needed it most. He introduced shared Storybook components, improved our review culture, and helped the team move from scattered patterns to something we could actually maintain across apps.
Strong senior engineer — especially good at modernizing legacy code without breaking production. The React and TypeScript migration was incremental, well planned, and the team learned a lot along the way.
Reliable in high-pressure environments. Delivered real-time interfaces under traffic, communicated clearly, and mentored juniors with patience. Would work with him again on any complex frontend initiative.
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Writing & Resources
Shareable notes and checklists from production React work — built to be useful, not just promotional.
Frontend Engineering Notes
Articles on React architecture, Next.js, migrations, and lessons from production teams.
Read the blogSenior Frontend Engineer Checklist
A shareable checklist distilled from production React work — with a free PDF download.
Open checklist07.
Get in Touch
Building something new, modernizing a frontend, or looking for a senior engineer? Let’s talk.