Senior Fullstack Engineer

 Company Overview

 Lean Tech is a rapidly expanding organization situated in Medellín, Colombia. We pride ourselves on possessing one of the most influential networks within software development and IT services for the entertainment, financial, and logistics sectors. Our corporate projections offer a multitude of opportunities for professionals to elevate their careers and experience substantial growth. Joining our team means engaging with expansive engineering teams across Latin America and the United States, contributing to cutting-edge developments in multiple industries. 

Position Title: Senior Full Stack Developer (React / Node.js / NestJS / Python)

Location: LATAM (Remote)

What We Are Looking For

We are looking for a Senior Full Stack Developer who can own projects end-to-end—from architecture design to deployment—and build scalable, cloud-native applications from scratch. You will work across the full stack using React on the frontend and Node.js/NestJS on the backend, define best practices, and integrate modern AI tooling and LLM-based agents into our products and development workflow. Fluent English is essential for daily communication with international teams.

Key Responsibilities

• Backend Development Build and maintain scalable backend services and RESTful APIs using Node.js and NestJS, following clean architecture and SOLID principles.

• Frontend Engineering Design and implement responsive, high-performance frontend applications using React (Hooks, Context API, advanced state management).

• Database & Caching Management Design and optimize SQL (PostgreSQL/MySQL) and NoSQL (MongoDB, DynamoDB) databases, implementing caching, pub/sub, and session management using Redis.

• Cloud Infrastructure & DevOps Architect cloud infrastructure on AWS (EC2, Lambda, S3, RDS, ECS/EKS, API Gateway, IAM), maintain CI/CD pipelines, and apply containerization and orchestration best practices (Docker, Kubernetes).

• AI Tooling & Agent Integration Utilize AI-assisted development tools (GitHub Copilot, Claude Code, Cursor) to accelerate delivery, and design/fine-tune LLM-based agents and AI workflows (RAG pipelines, prompt engineering, tool/function calling, vector databases).

• Code Quality & Testing Write clean, well-tested (unit, integration, E2E), and documented code while participating in code reviews and architecture discussions.

Must-Haves

• Experience 5+ years of proven experience as a Senior Full Stack Developer, building projects end-to-end from scratch.

• Frontend Core Advanced proficiency in React and its ecosystem (Hooks, Context API, state management via Redux, Zustand, or Context), alongside HTML5, CSS3, modern JavaScript (ES6+), and TypeScript.

• Backend Core Strong proficiency in Node.js and NestJS (modules, dependency injection, guards, interceptors, microservices architecture), with working proficiency in Python for building APIs (FastAPI/Flask), automation, or AI/LLM workflows.

• Databases & Cloud Solid experience with SQL and NoSQL databases, Redis, and deploying/managing applications on AWS using Infrastructure as Code (Terraform, AWS CDK, or CloudFormation).

• AI & LLM Ecosystem Daily hands-on experience using AI development tools, solid understanding of LLM agent development (prompt engineering, RAG, LangChain/LlamaIndex), and knowledge of vector databases (Pinecone, Weaviate, pgvector).

• Language Skills Fluent English (verbal and written) for clear communication within distributed teams.

Nice to Have

• Leadership Experience leading small teams or mentoring junior/mid-level developers.

• Certifications AWS certifications (Solutions Architect, Developer Associate, etc.).

• Advanced Tech Experience with GraphQL and Kubernetes at scale.

• Community Contributions to open-source projects.

Why You Will Love Lean Tech

• Join a powerful tech workforce helping change the world through technology.

• Professional development opportunities with international customers in a collaborative environment.

• Clear career path and mentorship programs designed to help you reach new levels.

Lean Tech is an equal opportunity employer. We celebrate diversity and are committed to creating an inclusive environment for all employees.