Lead Backend Engineer, Paris

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.

If you’re an experienced backend engineer who loves designing scalable systems, guiding technical decisions, and elevating team standards, this role is for you.

**Your Mission**:
As Lead Backend Engineer, you will be the technical lead of the backend team and a key contributor to the evolution of cozycozy’s architecture.

**Technical Leadership**:

- 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.

**Backend Architecture & System Ownership**:

- 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.

**Hands-On Development**:

- 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.

**Infrastructure, Automation & Reliability**:

- 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.

**Technical Processes & Standards**:

- 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.

**About You**:
You’re a strong backend engineer ready to evolve into a broader leadership role. You thrive in environments where you can combine coding, architecture, and mentorship.

You may be a great fit if you have:

- Strong experience with **Node.js + TypeScript** (Fastify, Express, Yarn, Zod, OpenAPI, Jest ) monorepo tooling is a plus.
- 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, and a mindset focused on continuously improving monitoring and insights.

**Bonus**:

- You have experience in travel/metasearch, marketplaces, or real-time large-scale systems.
- You are knowledgeable in React (Next.js) for cross-team collaboration.

**Why join Cozycozy?**:Have the opportunity to work on a global B2C platform with real user impact and high visibility.

Get involved in projects with strong technical challenges around high traffic, massive datasets, and performance-driven backend architecture.

Play a key role in optimizing systems and databases that reach trillions of rows and require top-tier speed.
- Collaborate and work in a flat structure where you have autonomy, ownership, and influence over key technical decisions.

Competitive salary, stock options, Alan health insurance, and Swile card.

**Our hiring process**:

- HR interview with Mia, our Head of Talent
- 1:1 interview with the Hiring Manager (onsite)
- Technical case to present your recommendations to the CEO and our stakeholders.
- Meet the team onsite