Senior FullStack Developer

Location: Paris, Île-de-France, France

Department: Research & Development

Workplace: hybrid

Employment Type: full

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.