Senior Fullstack Engineer — Remote/Paris Hybrid

CryptoNext Security; Paris; Hybride; EUR 90 000 - 130 000; Plein temps

Avantages offerts par ce poste

Competitive salary

Remote-friendly hybrid office in Paris

Career growth in deeptech cryptography

Résumé du poste

CryptoNext Security is a deeptech startup building post-quantum cryptography solutions for finance, defense, and telecom. The engineering team of six owns each feature across a single TypeScript monorepo, with three days in our Paris office and the rest remote.

You will design APIs, model data, and ship secure, testable code using modern tools and AI-assisted development. You will collaborate with Product and QA to deliver robust backend services and intuitive interfaces, while keeping builds

Qualifications

• Strong TypeScript across the stack: strict mode, generics, types shared between server and client instead of duplicated.
• Node.js backend: API design, auth, error handling, observability.
• Asynchronous processing: queue consumers and background workers, idempotency, retries and failure handling, backpressure.
• PostgreSQL: schema design, migrations and rollbacks, indexing, reading a query plan.
• Strong React: hooks, composition, clear state boundaries, client-side routing and server state caching.
• API contract design: REST, OpenAPI, typed clients, versioning.
• Unit and integration testing, with a defensible position on what belongs at which level and on what is worth testing at all.
• 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.

Responsabilités

• Own features end to end in TypeScript: Hono and Node.js on PostgreSQL, React SPA on the front.
• Design HTTP APIs consumed through Hono's typed RPC client, with generated OpenAPI specs.
• Model and query PostgreSQL: schema, migrations, query performance.
• Build interfaces with Vite, TanStack, Tailwind and shadcn/ui.
• Work directly with Product and QA.
• Write the unit and integration tests that back your features, and give QA what they need to automate the rest.
• Review code.
• Use AI coding tools as leverage under your own judgement, staying accountable for what lands in the repo.
• Propose upgrades and refactorings, and explain the trade-offs you accepted.

Connaissances

TypeScript

Node.js

Asynchronous processing

PostgreSQL

React

Frontend toolchain

API design

Testing

AI-assisted development

Senior mindset

Outils

Vite

TanStack

Tailwind

shadcn/ui

OpenAPI

Hono RPC

Go

Description du poste

CryptoNext Security is a deeptech startup building post-quantum cryptography solutions for finance, defense, and telecom. The engineering team of six owns each feature across a single TypeScript monorepo, with three days in our Paris office and the rest remote.

You will design APIs, model data, and ship secure, testable code using modern tools and AI-assisted development. You will collaborate with Product and QA to deliver robust backend services and intuitive interfaces, while keeping builds