Senior Go Developer - Integration

Cryptonext Security; Île-de-France; Hybrid; EUR 70,000 - 110,000; Full time

Job summary

CryptoNext Security SAS is a deeptech startup specializing in post-quantum cryptography. A team of engineers builds connectors in Go, linking CryptoNext Platform to client tools via REST APIs, while consuming diverse third‑party APIs with robust error handling.

The role emphasizes API design, OpenAPI contracts, asynchronous processing with RabbitMQ, and strong observability. Based in Île-de-France, the team operates in a hybrid model with three days in the Paris office and remote work for the

Qualifications

• Experience with Go and concurrent programming patterns.
• Experience with hexagonal architecture or equivalent modular design.
• Proficiency in integrating with third-party APIs and robust HTTP clients.
• Familiarity with asynchronous processing and message queues.
• Strong SQL skills with PostgreSQL and data modeling.
• Experience with Redis for caching and fast data access.
• Knowledge of API design, RESTful services and OpenAPI.
• Understanding of CI/CD pipelines and containerization.
• Ability to observe, instrument, and diagnose distributed systems.
• Experience with AI-assisted development in production codebases.

Responsibilities

• Build and maintain Go-based connectors between CryptoNext Platform and clients’ tools via REST APIs.
• Consume heterogeneous third‑party APIs with pagination, rate limits, retries and outages.
• Design and evolve API contracts using OpenAPI and versioning.
• Model and query PostgreSQL, use Redis, and process work asynchronously with RabbitMQ.
• Containerize deliverables with Docker/Docker Compose and integrate with GitLab CI.
• Instrument services with logs, metrics, traces and diagnose incidents in staging/production.
• Write unit and integration tests and support QA automation.
• Review code and onboard new team members.
• Collaborate with Product and QA; apply AI coding tools judiciously.
• Propose architecture changes and explain trade-offs.

Skills

Go

Hexagonal architecture

API integration

Asynchronous processing

PostgreSQL

Redis

REST APIs

CI/CD

Observability

AI in development

Tools

RabbitMQ

OpenAPI

PostgreSQL

Redis

Docker

Docker Compose

GitLab CI

Job description

Who we are

CryptoNext Security is a deeptech startup specializing in post-quantum cryptography. Our solutions help businesses and institutions prepare for a future where quantum computers will challenge traditional data security. We work with leading clients in finance, defense, and telecommunications.

On a daily basis, you will

• Build and maintain, in Go, the connectors that link CryptoNext Platform to our clients' tools (CLM, CMDB…): extracting, normalizing and exposing data through REST APIs.
• Consume heterogeneous third-party APIs: handle pagination, rate limits, retries, idempotency and provider outages.
• Design and evolve the API contracts exposed to CryptoNext Platform: OpenAPI and versioning.
• Model and query PostgreSQL, use Redis, and process work asynchronously through RabbitMQ.
• Containerize your deliverables (Dockerfile, Docker Compose) and get your changes through GitLab CI.
• Instrument your services (logs, metrics, traces), diagnose incidents in staging and production, and contribute to root cause analyses.
• Write the unit and integration tests that back your features, including against test doubles of provider APIs, and give QA what they need to automate the rest.
• Review code and help onboard new team members.
• Work directly with Product and QA.
• Use AI coding tools as leverage under your own judgement, staying accountable for what lands in the repo.
• Propose architecture changes and refactorings, and explain the trade-offs you accepted.

How we work

A team of six engineers, within our 15-person R&D department. Connectors live in a monorepo and follow a hexagonal architecture. Three days a week in our Paris office, the rest remote. Short feedback loops, high standards. We ship a working version early rather than polishing in isolation, and keep solutions as simple as the problem allows.

The skills you'll need

• Production Go: concurrency (goroutines, channels), context, explicit error handling, interfaces, modules and standard tooling (go test, go vet).
• Hexagonal architecture (ports and adapters), or the ability to defend an equivalent split.
• Third-party API integration: robust HTTP clients, timeouts, retries with backoff, pagination, rate limiting, idempotency.
• Asynchronous processing: RabbitMQ consumers, acknowledgements, retries and failure handling, dead-lettering, backpressure.
• PostgreSQL: schema design, migrations and rollbacks, indexing, reading a query plan. Hands-on use of Redis.
• API contract design: REST, OpenAPI, versioning.
• Unit and integration testing, with a defensible position on what belongs at which level and on what is worth testing at all.
• Delivery: Docker and Docker Compose, GitLab CI.
• Operations: observability and incident diagnosis.
• Real use of AI-assisted development in a production codebase: agentic workflows, context management, reviewing generated output as critically as a colleague's merge request. You have a view on where these tools pay off and where they create debt.
• Experience means you can say why you chose an approach, what you rejected, and what it will cost in six months.

Bonus skills

• Java.
• Knowledge of the CLM/PKI (X.509 model) and CMDB domains.
• Knowledge and hands-on handling of provider authentication schemes: OAuth2, mTLS, API keys.
• Secure coding practices and application security.
• Experience in a startup or deeptech environment.

The team you'll be joining

You will join a team of six engineers who own their features across the whole stack, inside our 15-person R&D department, working closely with Product and QA. You will report to the Head of Engineering and collaborate with other departments to build the backend services and interfaces our clients depend on.

Our recruitment process

Initial discussion with our HR team to explore your background and motivations.

Technical interview with a developer: a live coding session of 1 to 1.5 hours. AI coding tools are required, not merely allowed. We are interested in how you direct and review them. No take-home assignment.

Meeting with a manager to ensure alignment with our company culture.

If successful, you will receive a final offer!

What's in it for you at CryptoNext

• A stimulating work environment with cutting-edge technological challenges.
• A competitive salary, aligned with our compensation philosophy.
• A deep dive into the exciting world of post-quantum cryptography and cybersecurity.