Lead Backend Engineer, Paris

cozycozy.com; Paris; On-site; EUR 100,000 - 140,000; Full time

Benefits offered by this job

Stock options

Alan health insurance

Swile card

Job summary

Cozycozy in Paris is seeking a Lead Backend Engineer to steer the backend team and shape the platform's architecture. You will guide technical direction, mentor engineers, and own core backend systems powering millions of real-time accommodation results.

You will build high-quality TypeScript/Node.js and Go code, evolve REST/gRPC APIs, and partner with DevOps for scalable, observable infrastructure. Join a hands-on, collaborative environment focused on long-term reliability.

Qualifications

• Strong backend engineering background with leadership potential.
• Experience with Node.js/TypeScript and Go, or willingness to deepen Go skills.
• Deep understanding of modern databases and data pipelines.
• Proficiency with Docker, Kubernetes, and cloud/bare-metal deployments.
• Experience with event-driven systems and API design (REST/gRPC).
• Observability mindset with hands-on monitoring and incident response.

Responsibilities

• Lead backend topics and mentor engineers on architecture and code quality.
• Own core backend systems powering real-time results and large data flows.
• Design scalable services, ensure performance and reliability, drive RFCs.
• Develop high-quality TypeScript/Node.js and Go code and APIs.
• Collaborate with product, data, and frontend to ship improvements.
• Improve infra, CI/CD, monitoring, and incident response practices.

Skills

Node.js + TypeScript

Go programming

Distributed systems

Databases

Mentorship & leadership

REST & gRPC APIs

Observability & monitoring

Tools

Docker

Kubernetes

Grafana

Prometheus

Loki

Airflow

OpenAPI/Swagger

RabbitMQ

Kafka

MongoDB

PostgreSQL

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.

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.