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I'm a Senior Frontend Engineer with 11+ years of experience building scalable web apps and intuitive interfaces using React, Next.js, and Node.js. I've led microfrontend bridges for mobile apps, engineered a privacy-focused service network, and I'm currently building a fitness app powered by React Native. When I'm not fine-tuning my custom LLM or hitting the gym, I focus on delivering impactful solutions and collaborating with teams to raise the bar on performance and UX.…I'm a Senior Frontend Engineer with 11+ years of experience building scalable web apps and intuitive interfaces using React, Next.js, and Node.js. I've led microfrontend bridges for mobile apps, engineered a privacy-focused service network, and I'm currently building a fitness app powered by React Native. When I'm not fine-tuning my custom LLM or hitting the gym, I focus on delivering impactful solutions and collaborating with teams to raise the bar on performance and UX.

Andrei Constantinescu

Front-End Developer, Web Developer, Full Stack Developer, +4

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I'm a Senior Frontend Engineer with 11+ years of experience building scalable web apps and intuitive interfaces using React, Next.js, and Node.js. I've led microfrontend bridges for mobile apps, engineered a privacy-focused service network, and I'm currently building a fitness app powered by React Native. When I'm not fine-tuning my custom LLM or hitting the gym, I focus on delivering impactful solutions and collaborating with teams to raise the bar on performance and UX.…I'm a Senior Frontend Engineer with 11+ years of experience building scalable web apps and intuitive interfaces using React, Next.js, and Node.js. I've led microfrontend bridges for mobile apps, engineered a privacy-focused service network, and I'm currently building a fitness app powered by React Native. When I'm not fine-tuning my custom LLM or hitting the gym, I focus on delivering impactful solutions and collaborating with teams to raise the bar on performance and UX.

Available to hire

I’m a Senior Frontend Engineer with 11+ years of experience building scalable web apps and intuitive interfaces using React, Next.js, and Node.js. I’ve led microfrontend bridges for mobile apps, engineered a privacy-focused service network, and I’m currently building a fitness app powered by React Native.

When I’m not fine-tuning my custom LLM or hitting the gym, I focus on delivering impactful solutions and collaborating with teams to raise the bar on performance and UX.

Skills

Experience Level

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Work Experience

React Front End Developer at Citibank UK (Financial)

April 1, 2025 - Present

Rebuilt critical UI components for commodities trading workflows using modern React patterns and ag-Grid’s latest version, delivering a 35% faster, more responsive interface with complete feature parity. Architected performant React components with optimized rendering strategies for real-time market data, reducing unnecessary re-renders and significantly improving application responsiveness under high-frequency updates.

UI Developer at Balyasny Asset Management LLP (Financial)

October 1, 2022 - December 1, 2023

Built internal trading analysis tools using ReactJS, NextJS, GraphQL, and Ag-grid, improving interaction speeds by 25% and reducing bundle size by 20%. Contributed to a centralized monorepo, simplifying maintenance and ensuring consistent code and UI quality.

Software Consultant at BP Plc (Energy)

March 1, 2020 - March 1, 2021

Developed a framework-agnostic Payments SDK in TypeScript with 90% test coverage and built a ReactJS sandbox app to ensure reliability across payment scenarios. Enhanced security by implementing an AWS-based user login monitor with automated alerts and notifications.

Frontend Developer at Partners Capital LLP (Financial)

September 1, 2019 - March 1, 2020

Developed a ReactJS and TypeScript application, replacing Excel-based processes and improving responsiveness by 35% through optimized state management. Implemented an end-to-end testing regime with Cypress, ensuring feature reliability and system integrity.

Frontend Developer at UnlikelyAI

April 1, 2024 - May 1, 2024

Contract work delivering frontend development tasks.

Frontend Developer at CMC Markets Plc

July 1, 2021 - September 1, 2022

Contributed to trading platform UI improvements using ReactJS, NextJS, GraphQL, and Ag-grid; helped maintain a robust UI across markets and workflows.

Frontend Developer at Kaluza

June 1, 2019 - September 1, 2019

Front-end work focusing on payment and energy platform UI components.

Frontend Developer at NowTV (Sky UK)

November 1, 2018 - May 1, 2019

Front-end development for streaming and media platform features with a focus on performance and reliability.

Frontend Developer at uSwitch

August 1, 2018 - October 1, 2018

UI development work across product surfaces, delivering faster, more responsive experiences.

Frontend Developer at The Sun (News UK)

March 1, 2018 - August 1, 2018

Contributed to frontend projects delivering robust UI components and interactions.

Frontend Developer at AIG

November 1, 2017 - February 1, 2018

Front-end work delivering reliable UI features and components for enterprise applications.

Frontend Developer at Third Space Learning

August 1, 2017 - October 1, 2017

Front-end contributions to educational tooling with a focus on usability and performance.

Frontend Developer at Beamly

November 1, 2016 - August 1, 2017

UI development for social and media features, improving interactivity and performance.

Frontend Developer at Kano Computing

July 1, 2015 - October 1, 2016

Frontend development across education hardware/software projects, focusing on reliability and UX.

Frontend Developer at Learn Forward

April 1, 2014 - May 1, 2015

Early-career frontend work delivering modern UI components and interfaces.

UI Developer at UnlikelyAI (AI)

April 1, 2024 - May 1, 2024

Delivered front-end services for a chat-based application revamp, built a new UI with React and Tailwind; contributed to an interactive graph-based interface using canvas for data visualizations that effectively communicated complex information.

Software Consultant at CMC Markets Plc (Trading)

July 1, 2021 - September 1, 2022

Co-developed a ReactJS PWA investment app for internal customer support, enhancing digital customer engagement. Engineered seamless user flow integration into mobile native apps through microfrontend architecture, improving cross-platform consistency. Orchestrated native WKWebView views and SwiftUI integrations, balancing native responsiveness with web robustness. Elevated web performance within native apps by 30% and reduced bundle size by 20% via strategic tree shaking and code splitting.

Senior Frontend Developer at Kaluza (Energy)

June 1, 2019 - September 1, 2019

Pioneered the development of a real-time dashboard for smart device analytics, integrating with NodeJS and Kafka streams for live data feeds. Customized UK map visualizations using GeoJSON and WebGL, and employed D3.js for dynamic data representation. Curated a Storybook component library to streamline collaboration between design and development teams, enhancing UI consistency and development efficiency. Mentored junior team members, fostering knowledge transfer.

Senior Developer at NowTV (Sky UK) (Media)

November 1, 2018 - May 1, 2019

Collaborated in an agile setup to alleviate technical debt, achieving a 5% efficiency gain in content delivery pipelines across multiple devices. Enhanced testing protocols, leading to a 5% increase in coverage for both Jest unit tests and Ruby-based functional tests. Developed and deployed features such as a VOD content rail, and orchestrated a custom A/B testing framework using Optimizely.

Senior Frontend Developer at USwitch (Ecommerce)

August 1, 2018 - October 1, 2018

Integrated a 3D Secure verification process within the broadband switch journey, utilizing the Broadband Checker, resulting in a 15% uplift in conversion rates. Accelerated Cypress-based smoke test speeds by 40% by employing a record and replay strategy for API responses.

Full Stack Developer at The Sun (News UK) (Education)

March 1, 2018 - August 1, 2018

Developed interactive features such as live sports metrics and video galleries, significantly enhancing user engagement. Orchestrated the launch of the 2018 FIFA World Cup feature page, catering to peak viewership of over 2 million. Implemented performance optimizations and tracking enhancements, leading to more efficient ad loading via header bidding and granular insights into user metrics.

Frontend Developer at AIG (Insurance)

November 1, 2017 - February 1, 2018

Contributed to a contract-centric multi-tenancy insurance quote generation platform, enhancing business efficiency and customer service. Implemented Redux-Saga for effective management of asynchronous API interactions, ensuring a smooth user experience. Utilized memoization strategies to maintain optimal performance during the quote generation process.

Full Stack Developer at Third Space Learning (Education)

August 1, 2017 - October 1, 2017

Developed and optimized a suite of interactive React and Apollo-based educational applications, enhancing learning engagement and outcomes. Standardized front-end development with Styled-JSX, improving design consistency and streamlining UI component creation. Led the integration of GraphQL services, enabling real-time data exchange and dynamic content presentation.

Software Engineer at Beamly (Media)

November 1, 2016 - August 1, 2017

Orchestrated the front-end engineering of interactive marketing campaign platforms, driving user engagement and providing actionable insights through data analytics. Pioneered the adoption of responsive design methodologies, achieving seamless cross-platform user experiences and increasing campaign reach. Optimized page load times with advanced front-end optimization techniques, leading to a 30% improvement in performance metrics.

Software Engineer at Kano Computing (Education)

July 1, 2015 - October 1, 2016

Enhanced the user onboarding experience for the Kano web platform by streamlining the process with user-tested improvements. Co-developed the Kano web store with Vue.js, Shopify, and Node.js, enhancing e-commerce functionality and user interface. Implemented internal services like a delivery times estimator and a product bundler on top of Shopify, optimizing promotional activities for the marketing team.

Software Engineer at Learn Forward (Education)

April 1, 2014 - May 1, 2015

Contributed to the content team by crafting interactive and collaborative textbooks for students, utilizing Backbone.js, Jade, Stylus, and an open-source authoring tool. Played a pivotal role in the 2014 Romanian Presidential campaign by developing the website for candidate Monica Macovei, demonstrating proficiency in modern web development practices. Enhanced platform performance and usage tracking.