Senior Fullstack Developer – AI SaaS Builder

42Lab.co

Senior Fullstack Developer at 42Lab.co building impactful SaaS AI products from concept to delivery. Collaborate with founders to implement intelligent AI agents and maintain technical excellence.

Posted 7/19/2026full-timeValbonne • 🇫🇷 FranceSeniorWebsite

Core Competencies

Role fit

Core Competencies

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Demonstrates expertise in Fullstack Development, particularly with Next.js, React, and TypeScript, while effectively managing multiple projects and translating business needs into technical solutions. Proficient in integrating AI APIs and optimizing SaaS product shipping processes.

Highest-signal resume keywords

Fullstack DevelopmentNext.jsReactTypeScriptAI API Integration

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Hard Skills

Fullstack DevelopmentNext.jsReactTypeScriptPostgreSQLServerless ArchitecturesAI API IntegrationSaaS Product DevelopmentWorkflow AutomationProject Management

Soft Skills

Direct CommunicationAutonomyQuality FocusCollaborationProblem Solving

Industry Keywords

SaaSAI AgentsShipping ProcessesTechnical Decision MakingEntrepreneurial Vision

Tech Stack

Tools & technologies

JavaScriptNext.jsPostgresReactTypeScript

About the role

Key responsibilities & impact

Turn entrepreneurs' visions into high-impact products that gain traction
Build end-to-end SaaS products from A to Z in rapid sprints
Implement intelligent AI agents that automate complex workflows
Work directly with the founders to understand their vision and translate it into features that generate traction
Maintain our in-house boilerplate and contribute to the continuous improvement of our shipping processes
Manage two projects in parallel without sacrificing quality (yes, we’re ambitious)
Participate in strategic technical decisions that directly impact the success of our SaaS products

Requirements

What you’ll need

3+ years of fullstack development experience with production products
Deep expertise in Next.js, React, and TypeScript (you can code almost with your eyes closed)
Strong experience with PostgreSQL and serverless architectures
Proven ability to integrate AI APIs (OpenAI, Claude, embeddings, structured outputs, RAG, agnostic connectors, memory, etc.)
Full autonomy: you understand a business need and turn it into a technical solution without hand-holding
Shipping-obsessed: you prioritize working code in production over perfect code on localhost
Direct communicator: you can explain technical concepts to non-technical stakeholders without condescension

Benefits

Comp & perks

Maximum impact: your lines of code become real SaaS products
Modern stack: always using the latest technologies, zero technical debt, full technical freedom
No-bullshit culture: no pointless meetings, no corporate processes—just shipping
Elite team: work with A-players who challenge you and push you to improve
Attractive compensation: competitive package + bonuses tied to the success of the SaaS products you build
Long-term vision: opportunity to grow into a Lead Developer role
Ultra-fast hiring process: 30-minute call to validate fit