Senior Backend & AI Engineer — Node.js & MongoDB

Wellfound; Barcelona; Vor Ort; EUR 65.000 - 85.000; Vollzeit

Zusammenfassung

Migma, a budding AI email platform based in Barcelona, is seeking a backend engineer to join the two-person founding team. You will ship Node.js services and APIs, optimize MongoDB data models, and drive AI generation workflows end-to-end.

Work directly with the founders on infrastructure, integrations, and AI pipelines, balancing speed with reliability, security, and cost efficiency. Barcelona-based, in-office collaboration is required.

Qualifikationen

• Strong experience running Node.js backends in production.
• Practical MongoDB knowledge, including query performance, indexing, and data architecture.
• Experience shipping LLM-powered features or AI pipelines, with an understanding of their failure modes.
• Ability to explain how you measure AI output quality, latency, reliability, and cost.
• Strong API design, debugging, security, and problem-solving skills.
• Ownership, clear communication, and comfort working in a small team.
• Already based in Barcelona and able to work with the founding team in person.

Aufgaben

• Build and maintain Node.js services and APIs.
• Improve MongoDB queries, indexes, and data models.
• Develop AI generation workflows and improve the quality and consistency of their outputs.
• Handle queues, retries, rate limits, provider failures, and cost metering.
• Add useful monitoring and tests around critical workflows.
• Build product integrations and improve backend performance and reliability.

Kenntnisse

Node.js

MongoDB

API design

Security

Distributed systems

AI pipelines

Tools

Express

BullMQ

Redis

Python tooling

Jobbeschreibung

Barcelona, Spain · Full-time · Fully office-based
€65,000–€85,000 gross per year
Candidates must already be based in Barcelona. Visa sponsorship is not available.

Build the systems behind AI-powered email marketing.

Migma is building an AI platform that creates and sends on-brand email campaigns end to end. We are a two-person founding team in Barcelona, hiring a backend engineer with strong Node.js and MongoDB experience who has shipped AI features in production.

You will work directly with the founders on our APIs, infrastructure, integrations, and AI generation pipelines. We want someone who can ship quickly while making the system more reliable, understandable, and cost-efficient.

What you will do

• Build and maintain Node.js services and APIs.
• Improve MongoDB queries, indexes, and data models.
• Develop AI generation workflows and improve the quality and consistency of their outputs.
• Handle queues, retries, rate limits, provider failures, and cost metering.
• Add useful monitoring and tests around critical workflows.
• Build product integrations and improve backend performance and reliability.

What we need

• Strong experience running Node.js backends in production.
• Practical MongoDB knowledge, including query performance, indexing, and data architecture.
• Experience shipping LLM-powered features or AI pipelines, with an understanding of their failure modes.
• Ability to explain how you measure AI output quality, latency, reliability, and cost.
• Strong API design, debugging, security, and problem-solving skills.
• Ownership, clear communication, and comfort working in a small team.
• Already based in Barcelona and able to work with the founding team in person.

Our stack

Node.js, Express, MongoDB, Redis, BullMQ, and Python tooling; integrations with LLM providers and MCP. The product frontend uses Next.js, React, and TypeScript.

Useful extras

• Python services, structured LLM outputs, evaluations, agent workflows, or design-to-code generation.
• Stripe webhooks and idempotency, AWS SES and email delivery, or real-time systems.
• Shopify or Figma integrations, HTML email, React Email, or MJML.