Senior Software Engineer

Job Description

Help us build the leading wallet infrastructure for the multi-trillion-dollar digital asset industry. 

Dfns is a cybersecurity company providing crypto wallet infrastructure. Founded in August 2020 in Paris, Dfns was incubated by Techstars and STATION F before becoming a SOC-2 certified firm audited by Deloitte, employing 30 people across 6 countries and raising over $20M since creation with investors such as White Star Capital, Susquehanna, Coinbase, ABN AMRO, Hashed, 6MV, Semantic, Bpifrance, Figment, SGH, Wintermute, Motier, and more.

Dfns develops the most secure wallet-as-a-service infrastructure in Web3. It’s an API-first wallet management system, ideal for applications and organizations seeking to provide secure access to all blockchains through a single integration. Our APIs and SDKs were designed for wallet programmability and efficient implementations, enabling fast deployments, smart automation flows, as well as granular sets of permissions and policies via secure authentication credentials. 

Dfns is trusted by industry leaders such as Diageo, Warner Bros, Shopify, Casino, Lacoste, Breitling, Accor, FNAC, ABN AMRO, Fidelity, Ingenico, The Sandbox, Atari, Panerai, IWC, Richemont, Ba&sh, YSL, Belgium Government, Seychelles Government, London Metropolitan Police, Rihanna, Harry Styles, Justin Bieber, The Weeknd, David Guetta and more.

Join exceptional leaders (CTO, CPO, Chief Scientist) and experts (Platform Engineers, Security Engineers, Cryptographers, Protocol Designers) in a dynamic, collaborative environment. We’re looking for a skilled Senior Software Engineer with backend and API expertise, a keen eye for detail, and the ability to thrive in high-pressure situations within our engineering team.

As a Senior Software Engineer, you will create and implement functional software solutions. You will collaborate with upper management to define software requirements and lead operational and technical projects. You will oversee significant sub-departmental projects, relying on strong organizational and problem-solving abilities. You will also drive software change and release management processes to enhance the overall SDLC maturity. Ultimately, your goal is to ensure that software deliverables meet quality standards, adhere to timelines, and prioritize security.


  • Your main objective is to create, test, and maintain top-notch software that aligns with customer requirements and business objectives.
  • Your daily tasks will involve:
  • Contributing to Agile Scrum, ensuring deadlines and production quality.
  • Spearheading creative solutions for API and backend related challenges.
  • Managing platform infrastructure for scalability, high availability, and security.
  • Ensuring product scalability, high availability, and top-notch code quality.
  • Analyzing performance, identifying bottlenecks, and scaling backend systems.
  • Resolving complex issues by identifying root causes and implementing solutions.
  • Implementing robust logging, monitoring and alerting to maintain high availability.
  • Building, operating, and securing the APIs, backend, and even cloud infrastructure.
  • Incorporating security best practices into the API design and implementation.
  • Evaluating product code against specifications and gathering requirements.
  • Swiftly addressing problems and documenting all reported issues and actions taken.
  • Enhancing customer satisfaction through technical support.
  • Creating and updating internal and external documentation.
  • Collaborating with cross-functional teams to improve software development practices.
  • Staying updated on emerging technologies and suggesting improvements.
  • Participating in client meetings to assess our solution compared to market alternatives.

Preferred Experience

  • 6+ years as a Software Engineer.
  • Proficient in Typescript programming (or equivalent).
  • Proven experience designing secure APIs (RESTful, GraphQL).
  • Familiar with security vulnerabilities, encryption, and backend security best practices
  • Ensures product scalability, high availability, and code quality.
  • Identifies and optimizes performance bottlenecks, implementing caching.
  • Writes unit, integration, end-to-end, performance tests, and practice chaos engineering
  • Knowledgeable in SQL (PostgreSQL), NoSQL, and Redis
  • Knows how to design fault-tolerant backend systems using microservices, serverless, and distributed computing.
  • Hands-on experience with AWS services: Lambda, API Gateway, DynamoDB, S3, CloudFormation, CloudWatch, etc.
  • Experience in testing secure, resilient systems.
  • Strong problem-solving skills and ability to champion ideas.
  • Clear communication and clear thinking under high-pressure.
  • Entrepreneurial mindset with a professional demeanour.
  • [Bonus] Experience in developer tools, cybersecurity, or blockchain.
  • [Bonus] In-depth understanding of crypto wallets and their use cases.