Client Side Delivery: Senior Software Engineer - JavaScript

About VWO

VWO is a leading Digital Experience Optimization platform trusted by over 3,000 businesses in 100+ countries, including global brands like Samsung, Vodafone, Toyota, HBO, and Domino's. What began 15 years ago as one of the world’s first A/B testing tools has since evolved into a comprehensive, enterprise-grade platform used by product, marketing, and growth teams to experiment, personalize, analyze behavior, and build exceptional digital experiences.

Today, VWO offers a full-stack suite for A/B testing, multivariate testing, feature rollouts, heatmaps, session recordings, behavioural analytics, surveys, personalization, and more across web, mobile, and server-side applications — all in one unified platform. We enable teams to make confident, data-driven decisions that drive user engagement, retention, and conversion.

VWO is a profitable, founder-led business with $50M+ ARR, strong EBITDA margins, and a history of capital-efficient, sustainable growth. In January 2025, Everstone Capital acquired a majority stake in the company to help accelerate our global expansion — both organically and inorganically.

We are a fully remote team of 450+ people, with go-to-market teams across the Americas, Europe, and APAC, and product and engineering anchored in India. Our culture values deep thinking, fast execution, and strong ownership — with minimal bureaucracy and high autonomy. Despite our scale, we continue to operate with the agility and ambition of a startup.

As a Senior JavaScript Engineer, you will play a pivotal role in developing and maintaining high-performance JavaScript libraries that power all the core features of VWO. These libraries are deployed on our customers’ websites, directly impacting millions of users worldwide and enabling seamless digital experiences.

At Wingify, we have a deep passion for vanilla JavaScript and work with advanced technologies like TypeScript, Rollup.js, Cypress, and ESLint to build robust, scalable solutions.

We are unwavering in our commitment to Web Performance, constantly striving to optimize and innovate.

Discover some of our efforts here: https://engineering.wingify.com/posts/performance-improvements-in-vwo-smart-code

Job Responsibilities

• Develop and maintain core JavaScript libraries that serve as the backbone of our projects.
• Write clean, modular, and reusable code that can be leveraged across multiple JavaScript libraries and projects.
• Engage with the developer community by sharing your expertise and experiences through blog posts, open-source contributions, and discussions. Explore our Engineering Blog and GitHub page to see how we give back to the community.

Skills & Experience

Required Qualifications

• Experience: 3–6 years in software development with a strong focus on JavaScript.
• Proficiency: Expertise in Vanilla JavaScript, HTML, and CSS.
• TypeScript: Hands-on experience with TypeScript in production environments.
• Browser Knowledge: Deep understanding of browser internals, including the DOM, browser events, JavaScript APIs, and canvas rendering.
• Optimizations: A strong focus on delivering optimized content for fast user experiences.

Technical Expertise

• Knowledge of high-level programming concepts like Promises and data-binding.
• Experience writing modular, maintainable JavaScript code.
• Exceptional debugging skills to identify and resolve issues efficiently.
• Strong understanding of cross-browser compatibility and differences across modern and legacy browsers.

Testing & Automation

• A passion for writing automated tests to ensure reliability and stability across devices and browsers.
• Experience with testing frameworks such as Cypress or similar tools.

Soft Skills

• A mindset of continuous learning to stay updated with the ever-evolving front-end ecosystem.
• A collaborative attitude and willingness to share knowledge and improve team practices.

What We Value

• A passion for problem-solving and writing elegant, high-performance code.
• A keen interest in the latest advancements in web development technologies.
• A proactive approach to contributing to the broader engineering community.