Lead Full-Stack Engineer

Complexio
Cantabria, Spain
about 1 month ago
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Role details

Contract type
Permanent contract
Employment type
Full-time (> 32 hours)
Experience required
5 years minimum
Working hours
Regular working hours

Tech stack

Artificial Intelligence Architectural Patterns Software Product Management Software Architecture WebSocket Backend Low Latency Front End Software Development Restful APIs

Job description

Overview Complexio is building Stevie - an enterprise AI knowledge assistant that gives executives and operators a complete view of their organization through knowledge graphs.Our customers are large maritime shipping companies managing hundreds of vessels, thousands of daily emails, and complex commercial operations.We’re looking for a Senior or Lead Frontend Engineer to own Stevie’s frontend.The interface is the product - it determines whether enterprise customers trust the intelligence, get value quickly, and come back.You’ll shape all of that.Responsibilities Own the full frontend.No separate frontend team.You are it - with real influence on product direction and architectural decisions.Own the full frontend - conversational AI interfaces, content feeds, document generation, collaborative features.The product is evolving fast and you’ll shape what gets built and how.Must-haves 5+ years of frontend experience in production.You understand rendering models, performance characteristics, and architectural patterns deeply.Strong product sense.You push back when the UX doesn’t make sense.You’ve shipped real user-facing products.Real-time/streaming UI experience.Web Sockets, SSE, or similar live data patterns.Comfort with ambiguity.You take vague problems and turn them into concrete frontend solutions.You ship.End-to-end - prototype to production to iteration on feedback.Strong signals Enterprise/B2 B Saa S. You know the difference between consumer UX and building for a CFO who needs to trust a number.AI product experience.Latency UX, citation rendering, hallucination presentation.Design sensibility.Polished interfaces without a designer in the room.Backend literacy.You can read a REST API and collaborate with backend engineers on data contracts.Startup experience.Small teams, multiple hats, fast without cutting corners.How We Work Direct communication.Honest feedback, hard questions, no hiding behind process.Ownership over tasks.You’re asked what you shipped and learned, not to fill out status reports.Speed with quality.We ship fast because we scope well.Customer feedback cycles are weeks, not quarters.AI-augmented workflow.We use AI tools extensively and expect you to be comfortable with AI-assisted development.#J-*****-Ljbffr

Requirements

Must-haves 5+ years of frontend experience in production. You understand rendering models, performance characteristics, and architectural patterns deeply. Strong product sense. You push back when the UX doesn’t make sense. You’ve shipped real user-facing products. Real-time/streaming UI experience. Web Sockets, SSE, or similar live data patterns. Comfort with ambiguity. You take vague problems and turn them into concrete frontend solutions. You ship. End-to-end - prototype to production to iteration on feedback. Strong signals Enterprise/B2 B Saa S. You know the difference between consumer UX and building for a CFO who needs to trust a number. AI product experience. Latency UX, citation rendering, hallucination presentation. Design sensibility. Polished interfaces without a designer in the room. Backend literacy. You can read a REST API and collaborate with backend engineers on data contracts. Startup experience.

Benefits & conditions

Honest feedback, hard questions, no hiding behind process. Ownership over tasks. You’re asked what you shipped and learned, not to fill out status reports. Speed with quality. We ship fast because we scope well. Customer feedback cycles are weeks, not quarters. AI-augmented workflow. We use AI tools extensively and expect you to be comfortable with AI-assisted development. #J-*****-Ljbffr

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Good distractions

Talks and stories from around this role — technically off-topic, practically not.

1:52 min

Structuring and scaling the backend engineering team

Stefan Lingler Stefan Lingler +1 · Coffee With Developers

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Configuring live browser and WebSocket connection endpoints

Suchitra Swain Suchitra Swain · World Congress 2026 Europe

5:48 min

Balancing delivery latency with stream reliability and scale

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4:18 min

Prioritizing communication and structural awareness over strict tool mastery

Liam Hurrel +1 · World Congress 2021

1:38 min

Transitioning into backend engineering from web development

Stefan Lingler Stefan Lingler +1 · Coffee With Developers

3:37 min

Accessing API documentation and testing remote driving latency

Alexandru Ciinaru Alexandru Ciinaru +3 · World Congress 2025

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