# Senior FullStack Developer

> Cryptonext Security · Paris, France (Hybrid) · Full-time · Posted 2026-03-30

**Workplace:** hybrid

**Department:** Research & Development

## Description

### **Who we are**

CryptoNext Security is a deeptech startup specializing in **post-quantum cryptography**. We help institutions and enterprises prepare for a future where quantum computers will break current cryptographic standards.  
We work with major players in **finance, defense, and telecommunications**, delivering cutting-edge, quantum-safe security solutions.

### **On a daily basis, you will**

As a Full Stack Developer, you will contribute to the development of **DISCOVERY**, our next-generation observability and orchestration platform for post-quantum cryptography operations.

You will work across the entire stack — backend services, data flows, and frontend interfaces — collaborating closely with product, backend, and infrastructure teams.

### **Feature Development & Architecture**

-   Design, develop, and maintain **full-stack features** for the DISCOVERY platform.
-   Build modern, responsive **React** front-ends integrated with **Node.js** and **Kafka** backends.
-   Participate in architectural decisions and propose technical improvements aligned with long-term product vision.

### **Backend Engineering & APIs**

-   Design and implement **REST** and **event-driven APIs**.
-   Ensure performance, scalability, and resilience across distributed components.
-   Collaborate with backend engineers on domain modeling, API contracts, and data flows.

### **Observability & Data Visualization**

-   Implement advanced data visualization and monitoring features using the **ELK stack** (Elasticsearch, Logstash, Kibana).
-   Integrate backend logs, metrics, and analytics into frontend dashboards.

### **Engineering Excellence**

-   Participate in code reviews and uphold high engineering standards.
-   Contribute to technical documentation and promote software craftsmanship.
-   Apply KISS, DRY, SOLID, and pragmatic engineering principles (“done is better than perfect”).

### **DevOps & CI/CD**

-   Contribute to deployment workflows, CI/CD pipelines, and automation initiatives.
-   Work with Docker/Kubernetes-based environments to ensure smooth delivery.

## Requirements

### **The skills you'll need**

### **Must-have**

-   **10+ years** of experience in software development, ideally in a software editor or deeptech environment.
-   Master’s degree from a French engineering school or European equivalent.
-   Strong hands-on expertise in:

-   **Node.js**
-   **React**
-   **TypeScript**

-   Strong understanding of **Docker**, **Kubernetes**, and containerized deployments.
-   Experience with message-driven architectures (Kafka or equivalent).
-   Solid understanding of the **ELK stack** and its application in observability/analytics contexts.
-   Comfortable with **CI/CD**, Git workflows, automated testing, and modern DevOps practices.
-   Deep grasp of software design principles and maintainability.
-   Fluent in English.

### **Bonus**

-   Experience with **gRPC** or other microservice communication patterns.
-   Secure coding practices and application security awareness.
-   Experience with performance-critical or network-intensive systems.
-   Background in cybersecurity or cryptographic systems.
-   Experience with AWS, GCP, or Azure.

### **The team you’ll be joining**

You will join the **R&D engineering team** behind the DISCOVERY platform, collaborating with:

-   Backend engineers
-   Product managers
-   Platform and infrastructure engineers
-   The Head of Engineering
-   Cryptography experts and system engineers across the company

You will play a key role in shaping the architecture, user experience, and technical foundations of the DISCOVERY product.

### **Our recruitment process**

1.  **Introductory call** with HR — background, motivations, expectations.
2.  **Technical interview** with an R&D engineer, including a practical coding exercise.
3.  **Head of Engineering interview** — system design, long-term fit, and cultural alignment.
4.  **Offer & onboarding** — welcome to CryptoNext!

## Benefits

### **What’s in it for you at CryptoNext**

-   Join a fast-growing deeptech company at the cutting edge of quantum-safe cybersecurity.
-   Work on challenging engineering problems using modern technologies.
-   Build next-generation observability tools for cryptographic operations.
-   Flexible remote policy + office in central Paris.
-   Competitive compensation aligned with your seniority and expertise.
-   Direct impact on the future of secure communications.

## Apply

[Apply at Cryptonext Security](https://apply.workable.com/cryptonext-security/j/4649F30E84/apply)

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