Ilijan Kotarac
Ilijan Kotarac
Stack React · React Native · Node.JS
Speciality Architecture · Developer Experience · Team Leadership
Target Staff IC · Senior roles

Code that delivers results.

Philosophy

Context determines architecture.

A proof-of-concept glue-up deserves different scrutiny than a business-critical auth flow. I balance reliability, team capacity and the level of rigour to the stakes, avoiding over-engineering and under-investing.

Code is more than functionality.

Everybody knows the phrase that code is read ten times more than it's written. It’s a living document. I design systems where AI and humans can work consistently and without friction.

Leadership through doing.

Technical influence is earned, not assigned. I mentor via pair programming, guided debugging, and iterative learning. Architectural decisions that aren't owned by the whole team don't survive contact with a deadline.

Problem-solving at intersections

I thrive solving multifaceted challenges across technology, business constraints, innovative design and company culture, always aiming for simple, composable and maintainable solutions.

Portfolio

Checkout.com 2023 – 2024 Frontend Lead

Enterprise Authentication at Checkout.com

Frontend lead on authentication journeys for the enterprise dashboard at Checkout.com, used by clients including Netflix, Sony, and Klarna. Improved reliability through expanded E2E testing (Cypress + Cucumber), led debugging of an intermittent race condition in a third-party auth dependency, and avoided costly custom 2FA development through vendor library analysis and proof-of-concepts. Also built a React-based email template system later adopted across teams.

Lendio.com 2025 Freelance

2,000-Page WordPress to Webflow Migration for Lendio

Owned architecture and delivery of the migration of a 2,000-page SEO-critical marketing site from WordPress to Webflow. Designed custom data transformation pipelines to transform Gutenberg layouts into structured CMS data, enabling automated import and reducing manual effort from weeks to hours. Partnered with stakeholders to standardize higly variable layouts, implemented reusable design components, and added Percy-based visual regression testing to ensure safe releases.

Endava · Five Agency 2020 – 2022 Frontend Team Lead

Scaling Frontend Teams & Hiring

Engineering lead responsible for hiring and growing the frontend organization. Redesigned the interview process to better evaluate system design and project leadership, conducted 100+ interviews, and mentored senior engineers in interviewing. Introduced a structured team model with defined mentorship roles, enabling junior engineers to receive daily guidance while creating growth paths for senior engineers.

Supported the team through major organizational transitions: shift to remote-first work during COVID-19 pandemic and acquisition by Endava in 2021.

Endava · Five Agency 2020 – 2022 Frontend Team Lead

React & React Native Architecture Standardization

Defined the core architecture used across the company’s React and React Native projects and created showcase applications demonstrating best practices. Designed a hands-on onboarding course that introduced concepts such as dependency injection and the open–closed principle through iterative refactoring. Mentored senior engineers to guide new hires through the program.

GalaxyCon · Five Agency 2021 Frontend Team Lead

Real-time P2P video, audio & data with WebRTC for GalaxyCon

Owned frontend architecture for a complex real-time communication feature using WebRTC — including peer-to-peer video, audio, and data transfer.

Marriott International · Five Agency 2017 – 2019 Backend Engineer

100k-User Messenger Chatbot for Marriott

Co-architected a Facebook Messenger chatbot platform with over 100k users. Designed a custom markup language and parser enabling marketing teams to maintain hundreds of content pages without developer support. Built deployment pipeline using AWS Beanstalk. Reduced developer effort by 80% through content automation. Featured in Forbes.

Rosetta Stone · Five Agency 2016 Android Engineer

Rosetta Stone Language Learning Platform

Worked on the core lesson player, implementing QA strategies to cover thousands of possible states and developing custom shared element and ripple animations. Contributed to the award-winning app, recognized as Language Learning App of the Year (EdTech Breakthrough).

Expertise

Product Architecture

  • Frontend platform design
  • Micro-frontends & modular architectures
  • Distributed & real-time systems (WebRTC)
  • System decomposition & SOLID principles

Strategy

  • Trade-off analysis: off-the-shelf vs custom
  • Architecture for maintainability & AI-assisted development
  • Risk management
  • Gradual refactoring strategies

Engineering Leadership

  • Team growth, hiring, and mentorship
  • Onboarding & knowledge transfer
  • Technical influencing & cross-team alignment
  • Designing sustainable processes & culture

Full-stack Engineering & Reliability

  • React · React Native · Node.JS
  • Testing & QA strategies (unit, integration, E2E)
  • Performance optimization & scalability
  • Debugging and improving reliability in complex production systems

Contact

I'm looking for senior IC or staff engineering roles where architecture, team quality, and long-term thinking are taken seriously. If that sounds like your team, I'd like to hear from you.

Case studies and a deeper look at specific projects available on request.

ilijan.kotarac@gmail.com linkedin.com/in/ikotarac github.com/ikotarac
Ilijan Kotarac