Backend Engineer (Node.js/NestJS) — San Jose, Costa Rica
About Us
We are a stealth-mode startup building a new AI platform. Our mission is to make advanced language models deployable, customizable, and secure across diverse environments.
Role
We are seeking a Backend Engineer (Node.js/NestJS) to extend our platform using our existing codebase. You’ll build the proxy backend that interacts with our custom inference runtime and extend dashboards.
This role requires strong backend engineering skills, the ability to integrate existing systems, and comfort working closely with C++/CUDA engineers building low-level runtime features.
Responsibilities
Proxy Backend for Inference Runtime
- Build and maintain a Node.js-based proxy backend that:
Accepts inference requests from the frontend.
Schedules and serializes prompts.
Manages QKV cache load/unload.
Provides APIs to manage LoRA adapters.
Integrate with authentication, RBAC, and logging already provided by the existing stack.
Expose metrics and logs for monitoring inference usage and performance.
Dashboards
Extend the existing Dashboard with Dataset upload, training job view, model management, inference usage, request history, and adapter selection.
Reuse auth, billing, and user management code (Auth0, Stripe).
Add necessary backend endpoints to support new UI flows.
Core Stack & Infrastructure
Develop using NestJS as the main backend framework.
Work with PostgreSQL, Redis, and HashiCorp Vault for persistence, caching, and secrets.
Use Socket.IO for real-time updates (job status, inference progress).
Ensure secure integration with Stripe (billing) and Auth0 (identity).
Collaborate with DevOps on deployment pipelines (Proxmox, Docker, CI/CD).
Requirements
Strong experience with Node.js and NestJS framework.
Proficiency in PostgreSQL and Redis for persistence and caching.
Hands-on experience with Socket.IO or other WebSocket libraries.
Experience with secure configuration and secrets management (HashiCorp Vault preferred).
Comfortable working with microservices and integrating with existing codebases.
Strong debugging and systems thinking — able to reason about scheduling, state management, and concurrency.
Nice to Have
Experience integrating with AI runtimes (gRPC/REST backends for inference).
Experience with RAG and MCP.
Experience with authentication/authorization frameworks (Auth0, JWT, RBAC).
Familiarity with Stripe API or similar billing systems.
Contributions to backend open-source projects.
Experience with WebRTC.
Why Join
Extend a proven SaaS foundation into a new AI runtime platform.
Competitive compensation, equity potential.