Senior Full Stack Developer - AI Integration

Company Description

Xappex revolutionizes CRM data management by developing innovative tools that integrate seamlessly with Excel, Excel Online, and Google Sheets. Trusted by hundreds of thousands of users globally, Xappex ensures efficient and intuitive data handling processes that save time and enhance productivity. The company focuses on creating powerful admin tools that simplify complex tasks for CRM users. At Xappex, we are committed to delivering solutions that redefine how businesses interact with CRM data.

We are at an inflection point. Across our entire product line, we are actively integrating AI capabilities — from intelligent query generation and natural language data interactions to AI-assisted workflows that make our tools dramatically more powerful for CRM users. This is not a future roadmap item. It is happening now, and the person we hire will be central to it.

We are looking for a full-time Senior Full Stack Developer to join our team. You will help build and support the next generation of Google Sheets, Excel, and Microsoft 365 add-ins used by customers around the world — and you will play a key role in embedding AI into the core of everything we ship.

What You Will Do

• Work across the full stack to build scalable, high-performance distributed systems that deliver excellent user experiences and drive business growth
• Develop new features and infrastructure in response to evolving product and business needs
• Lead and contribute to our AI integration initiative — designing and building AI-powered features across our product suite, including natural language interfaces, LLM-backed automation, and intelligent data handling capabilities
• Evaluate, prototype, and integrate AI APIs (including Anthropic Claude and OpenAI) into production features used by hundreds of thousands of customers
• Take ownership of projects — from concept and design to deployment and iteration
• Ensure application performance, reliability, and scalability, maintaining high standards for code quality and architecture
• Contribute within an Agile environment, following best practices and continuously improving your skills
• Primarily work with JavaScript (ECMAScript 2025+), TypeScript, Node.js, React, and MySQL
• Collaborate with a distributed team across time zones using Slack, Jira, and audio/video calls

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• Actively leverage AI coding tools — including Claude Code and OpenAI Codex — to accelerate development, automate repetitive tasks, and raise the quality bar across the codebase
• Stay current with the AI landscape and bring new ideas, tools, and approaches to the team proactively

What You Will Bring

• 6+ years of experience in a similar full stack role (startup/product experience is a strong plus)
• Strong expertise in JavaScript (ECMAScript 2025+), TypeScript, Node.js, React, and MySQL
• Experience with modern UI frameworks (e.g., Fluent UI, MobX)
• Familiarity with AWS services (e.g., Lambda, DynamoDB)
• Hands-on experience with building AI-powered product features — integrating LLM APIs, designing prompts for production use, and shipping AI capabilities to real users
• Hands-on experience with AI-assisted development tools, including Claude Code and OpenAI Codex, and the ability to integrate them effectively into day-to-day engineering workflows
• Deep, genuine interest in the AI space — you follow model releases, read research updates, track the competitive landscape, and regularly experiment with emerging tools
• A strong point of view on how AI is reshaping software development and SaaS products, with the drive to bring that perspective to bear at Xappex
• The ability to translate AI capabilities into concrete product value — you can look at what LLMs can do today and immediately see how to make our users' lives better

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• Bachelor's degree in Computer Science, Engineering, IT, or a related field
• Fluency in English and Belarusian, or Russian
• A proactive, accountable problem-solver

The AI-Forward Mindset We're Looking For

AI is not a feature we are bolting on — it is becoming the backbone of how our products work and how our team operates. We are integrating AI across our entire product line: XL-Connector 365, G-Connector, Enabler4Sheets, and beyond. That means natural language querying of CRM data, AI-assisted data mapping, intelligent error handling, and much more on the roadmap.

We want someone who doesn't just tolerate AI tools — they are energized by them. You know the difference between GPT-4o and Claude Sonnet and when to use each. You've shipped something real using an LLM API, not just tinkered in a playground. You have opinions about prompt engineering, context windows, RAG, and agentic workflows — formed through hands-on experience, not just headlines. You follow Anthropic, OpenAI, Google DeepMind, and the open-source ecosystem closely, because you genuinely find it fascinating.

At Xappex, you will have real influence over how AI shapes our products for years to come. If you want to work somewhere that is actively building the future of AI-powered productivity tools — not planning to someday — this is the role.

Why Join Xappex

• Work on products used by hundreds of thousands of customers worldwide
• Be at the center of our AI transformation — this is a rare opportunity to shape how AI gets built into a mature, widely-used product suite from the ground up
• Be part of a lean, experienced, and collaborative team where your work has direct, visible impact
• Opportunity to own projects end-to-end — build, own, ship, and see your work in the hands of real users fast
• We actively invest in AI tooling, research, and experimentation — you will be encouraged and supported to stay at the cutting edge
• Flexible, remote, friendly work environment