Senior Full-Stack Product Engineer en Barcelona, España

About Longtail

Longtail is building an intelligent decision-streaming platform that helps airlines make smarter, faster commercial decisions in real time. Combining automation, proprietary algorithms, AI, and live data, our technology helps airlines optimize pricing, availability, and product flexibility across thousands of routes worldwide.

We're a fast-growing, international team solving complex, real-world problems at scale.

The Role

You’ll help build and evolve Sightline, Longtail's conversational analytics and intelligent alerting product, as it moves from beta to a scalable, production-ready platform.

This is a backend-focused full-stack role. You'll own features end to end: understanding customer problems, designing solutions, building and deploying them, and supporting them in production.

A key challenge on this team is building AI-native software customers can trust: turning customer intent into secure, observable, explainable, and repeatable production workflows.

We're looking for someone with 7+ years of backend/full-stack engineering experience, including time spent operating production systems, not just shipping them.

What You'll Do

• Design and build backend services, APIs, and customer-facing capabilities across Sightline's product and platform; including conversational analytics, intelligent alerting, reports and saved analyses, and AI-powered/agentic workflows
• Own features end to end, from customer problem through to production
• Build reliable, asynchronous workflows with orchestration, error handling, recovery, and observability baked in
• Integrate with data, analytics, and AI model platforms
• Design resilient systems that handle failures gracefully
• Contribute to the React frontend when a feature calls for it
• Improve testing, observability, security, and performance across the platform
• Make pragmatic technical decisions as the product evolves, and help shape engineering standards and architecture as we grow

Our Tech Stack

Backend: Java, Spring Boot, Python, FastAPI, MCP

Frontend: React, Vite, Zustand, Vitest, Nginx

AI & Data: Anthropic, OpenAI, OpenRouter, Databricks, PostgreSQL, Amazon Aurora

Infrastructure: AWS, Kubernetes, Docker, Terraform, Kong, Keycloak, OpenTelemetry, New Relic

What We're Looking For

You're a strong backend engineer who:

• Has built and operated production SaaS products
• Is comfortable contributing across the stack
• Has strong API, database, and SQL skills
• Understands distributed systems, asynchronous processing, and failure modes
• Cares about reliability, observability, security, and maintainability
• Enjoys owning features end to end and takes ownership of software beyond deployment
• Can turn ambiguous customer problems into pragmatic technical solutions
• Uses AI-assisted development tools such as Claude Code, OpenAI Codex, or similar, while applying strong engineering judgement

Nice to have:

experience with AI-native products, LLM applications, agents, or workflow orchestration; and/or experience in analytics, enterprise SaaS, pricing, travel, or aviation. Experience building AI agents is a plus, but strong engineering fundamentals matter more.

What Success Looks Like

Within your first few months, you'll:

• Ship a meaningful customer-facing capability
• Take ownership of a defined area of Sightline
• Improve the reliability or observability of an existing workflow
• Build a strong understanding of our architecture and customer needs

Working at Longtail

We're a collaborative, distributed team that values transparency, ownership, clear communication, and sustainable ways of working. You'll have the autonomy to make meaningful technical decisions, the context to understand why your work matters, and the responsibility to see what you build succeed in production.

We're committed to building a respectful and inclusive workplace where people can do their best work.

Compensation & Benefits

Competitive Package with base + bonus + equity + Benefits

• Private health insurance and Pension contribution
• Learning and Development budget
• Childcare
• transport and meal vouchers

Interview Process

Intro call -> Coding interview -> System Design -> AI-Assisted Coding Exercise -> Behavioural interview -> Offer.