Lucy Labs
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Backend Engineer

This role helps build Lucy, the proactive AI coach from Lucy Labs that lives on your desktop as a cloud-backed app, while the product is in development with design partners.

Builds the core services and APIs the product runs on.

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Planned work

About the role

At Lucy Labs, this role owns the purpose described below.

The Backend Engineer at Lucy Labs builds the core systems, services, and APIs that power the Lucy Labs platform. This role owns backend architecture and implementation that enables AI-driven workflows, real-time coaching, secure data flow, and scalable product features. Backend Engineers are responsible for building reliable, high-performance systems that support fast product iteration and global scale.

This role is hands-on and impact-driven—focused on delivering backend systems that enable product velocity and user value.

The mission

At Lucy Labs, this role's mission is defined by the outcome and work below.

Build backend foundations that:

  • Power AI-assisted productivity workflows
  • Enable fast and reliable product delivery
  • Scale securely and efficiently
  • Support cross-platform applications (desktop + cloud)
  • Deliver data and system integrity at scale

What you'd own

At Lucy Labs, this role turns its mission into concrete responsibilities in each area.

1. API & Service Development

For 1. API & Service Development, Lucy Labs expects this role to own the responsibilities below.

  • Design and build REST/gRPC/GraphQL APIs
  • Develop scalable backend services and microservices
  • Enable high-throughput data operations
  • Collaborate with frontend/product teams on API clarity

2. System Architecture & Design

For 2. System Architecture & Design, Lucy Labs expects this role to own the responsibilities below.

  • Contribute to backend architecture decisions
  • Design modular, maintainable systems
  • Implement clean service contracts and data flows
  • Balance speed with architectural quality

3. AI Integration Support

For 3. AI Integration Support, Lucy Labs expects this role to own the responsibilities below.

  • Build backend components supporting AI orchestration
  • Integrate with AI services, vector databases, and RAG pipelines
  • Support contextual memory and workflow intelligence
  • Implement AI usage logging, fallback logic, and guardrails

4. Reliability, Security & Performance

For 4. Reliability, Security & Performance, Lucy Labs expects this role to own the responsibilities below.

  • Build with reliability, uptime, and observability in mind
  • Implement security best practices (auth, encryption, access control)
  • Improve system performance and latency
  • Develop and maintain automated tests and monitoring

What success looks like

Lucy Labs defines these milestones as role outcomes, not metrics for measuring the person.

60 days
Contributes to core backend services
90 days
Owns a backend domain or service
6 months
Improves backend performance + reliability
12 months
Enables major product capabilities at scale

Experience and fit

Lucy Labs looks for the essential experience listed here and treats the rest as helpful, not an automatic barrier.

Must have

  • 5+ years backend engineering experience
  • Node.js/TypeScript expertise (our primary stack)
  • PostgreSQL - SQL optimization, complex queries, schema design
  • RESTful API design - clean service contracts, versioning
  • AWS - EC2, RDS, S3, Lambda
  • Security best practices (auth, encryption, access control)
  • Experience building APIs and backend services

Nice to have

  • Multi-tenant SaaS architecture experience
  • GDPR compliance knowledge
  • High-scale systems (1M+ users)
  • Experience with AI/ML infrastructure
  • Message queues/event-driven systems (Kafka, Redis, etc.)
  • Vector databases (pgvector, Pinecone, Weaviate)
  • Startup or 0→1 product build experience

How you work

Lucy Labs looks for these working traits alongside technical experience.

Role DNA

Lucy Labs evaluates these traits as part of the fit for this role.

  • Systems thinker
  • Builder mindset
  • Clarity-driven engineer
  • Ownership mentality
  • Practical problem-solver

Leadership principles for the role

Lucy Labs expects this role to apply the following leadership principles.

  • Build for clarity and simplicity
  • Reliability is not optional
  • Speed with purpose
  • Own the system end-to-end
  • Architecture follows value
Next step

Apply for this role

The Lucy Labs application form opens with this role already selected. You can review the message before sending it.

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Frequently asked questions

Is this role open at Lucy Labs?

Yes. Lucy Labs confirmed this role is open on 25 August 2026.

Where does Lucy Labs base this role?

Lucy Labs bases this role in Madrid, Spain. The exact working arrangement is confirmed during the application conversation.

What does this role own at Lucy Labs?

At Lucy Labs, this role has one central responsibility: Builds the core services and APIs the product runs on. The full description sets out the mission, responsibilities, and relevant experience.

How do I apply to Lucy Labs?

At Lucy Labs, use the application form. The role is selected automatically, and you can review it before sending.

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