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cozycozy Logo cozycozy · IT - Software Development

Lead Backend Engineer

France, Paris · Job Posted March 01, 2026
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Job Description

At cozycozy, we’re building the world’s best accommodation metasearch platform, making travel simple, transparent, and inspiring. We already process millions of searches every month and we’re growing fast. To support this growth, we’re looking for a Lead Backend Engineer who will take technical ownership of our backend ecosystem, mentor the engineering team, and act as a key partner to the Head of Engineering on architecture, reliability, and system evolution.

Job Responsibility

  • Act as the reference engineer for backend topics, supporting the Head of Engineering in driving technical direction
  • Mentor senior and mid-level engineers, helping them grow through guidance on architecture, best practices, and code quality
  • Lead technical discussions, design reviews, and RFC processes
  • Own core backend systems powering millions of real-time accommodation results
  • Design and maintain scalable, low-latency services ingesting large volumes of data from dozens of partners
  • Contribute to key architecture decisions and ensure alignment with long-term platform goals
  • Ensure reliability, performance, and observability across backend components
  • Write high-quality TypeScript/Node.js and Go code while supporting continuous delivery of new features
  • Evolve our APIs (REST, gRPC, OpenAPI) to improve speed and performance
  • Work closely with product, data, and frontend to deliver user-impacting improvements
  • Partner with DevOps to improve our K8s, Docker, and bare-metal infrastructure (Linux, K3s, CI/CD)
  • Implement monitoring & alerting using Grafana, Prometheus, Loki
  • Improve performance, caching, resilience, and horizontal scalability of our systems
  • Help define coding standards, testing strategy, and workflow improvements
  • Advocate for strong documentation, observability, and long-term maintainability
  • Support incident response and help shape reliability practices across the team

Requirements

  • Strong experience with Node.js + TypeScript (Fastify, Express, Yarn, Zod, OpenAPI, Jest)
  • Solid experience with Go (Gin, Zap, code generators) or willingness to deepen your Go skills
  • Deep understanding of databases: MongoDB, PostgreSQL, Redis/Dragonfly and know Functional Programming Principles
  • Strong experience with Docker, Kubernetes, and cloud/bare-metal deployments (Linux, K3s)
  • Experience with queues & event-driven systems (RabbitMQ, Google Pub/Sub, Kafka)
  • Experience building and maintaining REST (OpenAPI, Swagger), gRPC APIs
  • Confidence working on big data pipelines, collaborating with data engineers, and creating scheduled jobs with Airflow or k8s Cronjobs
  • Observability-driven engineer with hands-on experience in Grafana, Prometheus, Loki, and Promtail

Nice to have

  • Experience in travel/metasearch, marketplaces, or real-time large-scale systems
  • Knowledgeable in React (Next.js) for cross-team collaboration

What we offer

  • Competitive salary
  • Stock options
  • Alan health insurance
  • Swile card
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