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

•     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.

How we work

A team of six engineers, within our 15-person R&D department. A single TypeScript monorepo, with shared types and tooling across services and front. 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. Our products ship on-premise, sometimes into air-gapped environments, so builds have to be reproducible and dependencies deliberate. We build software our clients rely on for security: secure defaults, reviewed dependencies and tested code are part of shipping, not a later phase. We care more about a decision you can justify than a pattern you can name.

The skills you'll need

•     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.

•     Comfortable with a modern frontend toolchain: fast bundling, utility-first styling, component libraries you extend rather than fight.

•     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. You have a view on where these tools pay off and where they create debt.

•     Seniority means you can say why you chose an approach, what you rejected, and what it will cost in six months.

Bonus skills

•     Go, used in parts of our codebase.

•     Hono typed RPC and end-to-end type inference.

•     Secure coding practices and application security.

•     Basic understanding of cryptography and cybersecurity.

•     Experience in a startup or deeptech environment.