Senior React Native Engineer, Secure communication & Payment

Job Openings Senior React Native Engineer, Secure communication & Payment,

King Deux Search & Consulting is a specialised executive search firm which offers bespoke talent solutions across financial services and commerce. We are committed to not only finding the right opportunity for our candidates but also leaving a legacy that lives on beyond the hiring process.

King Deux is partnering with an ambitious, self-financed start-up with our founders having an entrepreneurial background in AI, Hedge Funds, Biotech and Energy Production. Headquartered in London with our technical team based across the UK and France. We're looking for a Senior React Native Engineer to play a key role in building, improving and scaling our encrypted email app,

C.Email and also lead core development of the product itself.

You’ll work closely with CTO, cryptography specialist, and engineers to deliver a high-performing, secure, and intuitive product.

This is a hands-on engineering role with end-to-end ownership — from development and testing to deployment and user experience improvements. You’ll be instrumental in shaping how millions of users communicate securely.

Lead core development of new features from concept to release, owning them end-to-end — from design discussions and prototyping through to testing and deployment

Develop and enhance the

C.Email mobile app using React Native (Expo + CNG).

Improve app stability and performance; resolve bugs and add UI improvements.

Implement cryptography improvements for performance and integration.

Write modular, testable, maintainable code with clear documentation.

Participate in daily stand-ups and code reviews, sharing best practices and ideas.

4-6 years experience in software engineering; strong background in React Nativeand Type Script.

Experience setting up automated tests from scratch — unit, component, and user-simulation tests.

Strong understanding of mobile-first architecture (local data storage, offline-first).

Experience working in startups or small technical teams (series A or B/ pre VC funding).

Experience working with email standards and protocols (e.g. MIME, Gmail API) is a plus.

React Native (Expo) – advanced development and optimisation.

Kotlin / Swift – for native components. Go – used for cryptography

C++ – for performance improvements and interface integration (secondary priority).

GCP / AWS (light) – basic infrastructure setup and management (SES, AWS lambda, Redis, RDS, EC2 autoscaling)

Familiarity with cryptographic principles (key exchange, signing, encryption).

Interested parties, please send your CV directly to  or apply directly.

Please note that only shortlisted applicants will be contacted.