We are a u.s.based saas startup looking for a senior full stack mern developer to work directly with our hands-on cto.this is a senior role for someone who can not only ship features but also improve architecture, enforce clean code practices, and scale an mvp into a production-grade saas platform.*what you'll do*:- take ownership of an existing mern mvp and evolve it into a scalable, production-ready product- refactor and improve messy or inefficient code for clarity, maintainability, and performance- debug and resolve complex cross-layer issues quickly (mongodb, node.js, react, ci/cd)- design and optimize mongodb schemas, indexes, atlas search, and triggers- build event-driven workflows with mongodb triggers)- integrate ai/llm services (openai, aws comprehend, embeddings, nlp features) into production apps- support and improve twilio-based messaging and webhook integrations- contribute to new product features end-to-end (backend + frontend)*requirements*:- expert in mern stack: mongodb, express.js, react.js, node.js- deep mongodb knowledge (indexes, performance, aggregation, triggers)- strong backend/infra skills: node.js async/memory, aws (ec2, s3, lambda), ci/cd pipelines- experience integrating ai services into production apps- excellent english communication (mandatory)- availability during u.s. West coast working hours (pst/pdt)- based in argentina or brazil*benefits*:- direct collaboration with a technical founder/cto- long-term role solving real production challenges (not just crud apps)- remote role with u.s. time zone collaboration- opportunity to grow into a lead role as the team expands