Senior Software Engineer

Dfns; Paris; Hybrid; EUR 125,000 - 214,000; Full time

Benefits offered by this job

Healthcare

Stock options

Remote-first

Job summary

Dfns is seeking a Senior Software Engineer to design and scale core backend services powering our fintech platform. You’ll build REST APIs, microservices, and data infrastructure, and push for production-readiness, security, and performance.

You’ll work with product, security, and infrastructure teams to solve complex problems across wallets and cross-chain integrations, contributing to architecture decisions and improving developer workflows.

Qualifications

• 8+ years of backend software engineering experience in fintech or finance.
• Strong in TypeScript, proven track record building scalable APIs and dev tools.
• Expertise with databases (PostgreSQL, DynamoDB, NoSQL) and AWS services.
• Skilled in microservices, CI/CD pipelines, observability, and SSLDC practices.
• Familiar with public key infrastructure and backend security fundamentals.
• Strong problem-solving, clear communication, and ability to deliver under pressure.

Responsibilities

• Design, build, and maintain secure, scalable backend services and APIs (REST).
• Architect databases and microservices for performance, reliability, and growth.
• Own projects end to end: from requests, implementation to production and iteration.
• Troubleshoot complex issues, resolve performance bottlenecks, ensure resilience.
• Collaborate with product, security, and leadership on roadmap and technical direction.
• Document systems, share knowledge, and support client-facing discussions.

Skills

Backend API design

TypeScript

Scalable architectures

Databases

AWS

CI/CD

Security fundamentals

Job description

Join a team of engineers and cryptographers building the infrastructure behind the next generation of financial systems.

We’re hiring a Senior Software Engineer to build and scale the core backend services that power our platform. You’ll design and operate APIs, microservices, and data systems that handle wallet operations, transaction processing, and integrations across multiple blockchains. You’ll work closely with product, security, and infrastructure teams to turn complex requirements into reliable production systems. This role goes beyond implementation. You’ll contribute to architecture decisions, improve development workflows, and help ensure the platform remains fast, secure, and resilient under real-world financial workloads.

Responsibilities

• Design, build, and maintain secure, scalable backend services and APIs (REST).

• Architect databases and microservices for performance, reliability, and growth.

• Own projects end to end: from requests, implementation to production and iteration.

• Troubleshoot complex issues, resolve performance bottlenecks, ensure resilience.

• Collaborate with product, security, and leadership on roadmap and technical direction.

• Document systems, share knowledge, and support client-facing discussions.

Requirements

• 8+ years of backend software engineering experience in fintech or finance.

• Strong in TypeScript, proven track record building scalable APIs and dev tools.

• Expertise with databases (PostgreSQL, DynamoDB, NoSQL) and AWS services.

• Skilled in microservices, CI/CD pipelines, observability, and SSLDC practices.

• Familiar with public key infrastructure and backend security fundamentals.

• Strong problem-solving, clear communication, and ability to deliver under pressure.

Recruiting Process

• Intro call with Co-CEO (30 min)

• Personality and cognitive tests (45 min)

• Coding test in the language of your choice

• Focus interviews with the hiring panel (180 min)

  • Code review

  • Architecture review

  • Security fundamentals

  • Culture check fit

• Final interview with CTO (30 min)

• Reference calls and background checks

Terms

• Title: Senior Software Engineer

• Salary: $140,000-240,000 per year (full-time).

• Equity: 100-200 stock options vested over 4 years.

• Benefits: Healthcare and travel expenses.

• Location: US or EU (remote-first, office optional).

• Equipment: MacBook Pro + essentials.