Full Stack Developer – MERN Stack

We're looking for an experienced Full-Stack Engineer who can architect and build AI-powered agent systems from the ground up. You'll work across the entire stack—from designing scalable backend services and LLM orchestration pipelines to creating frontend interfaces for agent interactions through widgets, bots, plugins, and browser extensions.

You should be fluent in modern backend technologies, AI/LLM integration patterns, and frontend development, with strong systems design thinking and the ability to navigate the complexities of building reliable AI applications.

Note: This is an on-site, 6-day-a-week role. We are in a critical product development phase where sthe peed of iteration directly determines market success. At this early stage, speed of execution and clarity of thought are our strongest moats, and we are doubling down on both as we build through our 0→1 journey.

WHAT YOU BRING:

You take ownership of complex technical challenges end to end, from system architecture to deployment, and thrive in a lean team where every person is a builder. You maintain a strong bias for action, moving quickly to prototype and validate AI agent capabilities while building production-grade systems. You consistently deliver reliable, scalable solutions that leverage AI effectively — whether it's designing robust prompt chains, implementing RAG systems, building conversational interfaces, or creating seamless browser extensions.

You earn trust through technical depth, reliable execution, and the ability to bridge AI capabilities with practical business needs. Above all, you are obsessed with building intelligent systems that actually work. You think deeply about system reliability, performance, cost optimization, and you're motivated by creating AI experiences that deliver real value to our enterprise customers.

WHAT YOU WILL DO:

Your primary responsibility (95% of your time) will be designing and building AI agent systems across the full stack. Specifically, you will:

• Architect and implement scalable backend services for AI agent orchestration, including LLM integration, prompt management, context handling, and conversation state management.
• Design and build robust AI pipelines — implementing RAG systems, agent workflows, tool calling, and chain-of-thought reasoning patterns.
• Develop frontend interfaces for AI interactions including embeddable widgets, Chrome extensions, chat interfaces, and integration plugins for third-party platforms.
• Optimize LLM operations — managing token usage, implementing caching strategies, handling rate limits, and building evaluation frameworks for agent performance.
• Build observability and monitoring systems for AI agents, including prompt versioning, conversation analytics, and quality assurance pipelines.
• Collaborate on system design decisions around AI infrastructure, model selection, vector databases, and real-time agent capabilities.
• Stay current with AI/LLM developments and pragmatically adopt new techniques (function calling, multi-agent systems, advanced prompting strategies) where they add value.

BASIC QUALIFICATIONS:

• 4–6 years of full-stack development experience, with at least 1 year working with LLMs and AI systems.
• Strong backend engineering skills: proficiency in Node.js, Python, or similar; experience with API design, database systems, and distributed architectures.
• Hands-on AI/LLM experience: prompt engineering, working with OpenAI/Anthropic/Google APIs, implementing RAG, managing context windows, and optimizing for latency/cost.
• Frontend development capabilities: JavaScript/TypeScript, React or Vue, browser extension development, and building embeddable widgets.
• Systems design thinking: ability to architect scalable, fault-tolerant systems that handle the unique challenges of AI applications (non-determinism, latency, cost).
• Experience with AI operations: prompt versioning, A/B testing for prompts, monitoring agent behavior, and implementing guardrails.
• Understanding of vector databases, embedding models, and semantic search implementations.
• Comfortable working in fast-moving, startup-style environments with high ownership.

PREFERRED QUALIFICATIONS:

• Experience with advanced LLM techniques: fine-tuning, function calling, agent frameworks (LangChain, LlamaIndex, AutoGPT patterns).
• Familiarity with ML ops tools and practices for production AI systems.
• Prior work on conversational AI, chatbots, or virtual assistants at scale.
• Experience with real-time systems, WebSockets, and streaming responses.
• Knowledge of browser automation, web scraping, or RPA technologies.
• Experience with multi-tenant SaaS architectures and enterprise security requirements.
• Contributions to open-source AI/LLM projects or published work in the field.

WHAT WE OFFER:

• Competitive salary + meaningful equity.
• High ownership and the opportunity to shape product direction.
• Direct impact on cutting-edge AI product development.
• A collaborative team that values clarity, autonomy, and velocity.

Based on experience, developers will be responsible for building various elements of a music app for an international client. Urgent requirement and immediate joining as project is already underway.

Job Title: Full Stack Developer

Company: Fortmindz

Location: Kolkata, India

About Fortmindz:

Fortmindz is a cutting-edge software development company that specializes in delivering innovative and intuitive mobile applications. We are looking for a talented Full Stack Developer to join our team and help us build world-class applications.

Responsibilities:

• Develop, test, and deploy web applications using both front-end and back-end technologies
• Collaborate with cross-functional teams to define, design, and ship new features
• Write clean, efficient, and maintainable code
• Troubleshoot and debug applications to optimize performance and user experience
• Stay up-to-date with new technologies, frameworks, and industry best practices
• Participate in code reviews and contribute to the continuous improvement of our development process

Requirements:

• Bachelor's or Master's degree in Computer Science or a related field
• At least 3 years of experience as a Full Stack Developer or in a similar role
• Strong knowledge of HTML, CSS, and JavaScript
• Experience with at least one of the popular front-end frameworks such as React, Angular, or Vue.js
• Experience with at least one of the popular back-end frameworks such as Node.js + Express Js, Laravel, Ruby on Rails, or Django
• Familiarity with Git and agile development methodologies
• Good understanding of RESTful APIs and web services
• Excellent problem-solving and debugging skills
• Strong communication and teamwork skills

Benefits:

• Competitive salary and benefits package
• Opportunities for career growth and professional development
• A dynamic and inclusive work environment
• Access to cutting-edge technologies and tools

If you are a talented Full Stack Developer who is passionate about building high-quality web applications, we would love to hear from you! Please submit your resume and a cover letter highlighting your relevant experience.

Fortmindz is an equal opportunity employer and values diversity at our company. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status.

Essential Duties & Responsibilities

● Design, build and maintain efficient, reusable, and reliable Ruby code
● Contribute to building an agile environment
● Test your code
● Engaged in all aspects of product development and will be working closely with product management, operations, client-engineering and customer success teams
● Working with an exceptional team to help scale a fast-paced business.
● Ability to work independently on challenging compound problems as well as collaborating with other team members to solve major goals
● Present complex ideas and approaches in simple communicable terms across engineering and management levels
● Identify bottlenecks and bugs, and devise solutions to these problems


Required Qualifications 

● Ruby on Rails (6+ years)
● PostgreSQL or MySQL
● JavaScript and AngularJS (or other client-side frameworks like Ember, Backbone, etc)
● Test-driven development with RSpec, Capybara, Jasmine
● Git, Continuous Integration, AWS, etc
● Bonus points for SaaS experience