Freelance Senior Software Engineer (Ruby on Rails) M/F/X

Trustpair; Paris; On-site; EUR 111,000 - 166,000; Full time

Job summary

Trustpair in Paris is seeking a senior backend engineer (Ruby on Rails) for a freelance contract. You will design and implement scalable features, collaborate across squads, and help deliver secure payment-focused services.

You’ll work in an autonomous engineering culture, participate in the SDLC, and mentor others while adopting AI-driven tooling. English required; EU-based candidates welcomed.

Qualifications

• 5+ years of Ruby (Rails) back end development experience.
• Ability to conceive the technical design of a complex product feature.
• Experience on a rapidly growing product with scalable architectures.
• Experience working in an Agile environment (Scrum or Kanban).
• Experience in API development with emphasis on resilience, scalability and security.

Responsibilities

• Lead the design of innovative features with high code quality.
• Contribute to the full SDLC, including architecture, coding, and releases.
• Support critical services to ensure secure payments.
• Monitor the tech landscape and propose improvements to the stack.
• Promote engineering excellence through code reviews, TDD, and mentoring.

Skills

Ruby on Rails

Architectural design

Agile (Scrum/Kanban)

API development

English fluency

Tools

Docker

AWS

GitLab CI

Job description

About

Trustpair stops vendor fraud before it happens. We're the automated vendor validation platform protecting 400+ enterprise companies worldwide. Since 2017, finance and procurement teams have used Trustpair to eliminate vendor fraud while reclaiming 90% of the time they once spent on manual checks. As vendor fraud grows more sophisticated, we stay ahead by combining deep expertise in financial crime with cutting‑edge technology. Our core product focuses on secure, reliable vendor account validation to wipe out fraud and boost efficiency. Internally, teams across Trustpair use AI tools in their day‑to‑day work to automate repetitive tasks and unlock strategic insights that help us build and operate better. From day one, you’ll be encouraged and trained to integrate these tools into your workflow in a practical, hands‑on way. With offices in New York, Paris, London, and Milan, we’re a diverse team united by a bias for action. We ship fast, learn from experiments, and tackle problems that matter: protecting billions in payments for companies worldwide. If you want to see your work make an immediate impact in financial security, Trustpair is built for you. Learn more about how we use AI in everyday work here.

Job Description

Trustpair stops vendor fraud before it happens. We're the automated vendor validation platform protecting 600+ enterprise companies worldwide. Since 2017, finance and procurement teams have used Trustpair to eliminate vendor fraud while reclaiming 90% of the time they once spent on manual checks. As vendor fraud grows more sophisticated, we stay ahead by combining deep expertise in financial crime with cutting‑edge technology. Our core product focuses on secure, reliable vendor account validation to wipe out fraud and boost efficiency. Internally, teams across Trustpair use AI tools in their day‑to‑day work to automate repetitive tasks and unlock strategic insights that help us build and operate better. From day one, you’ll be encouraged and trained to integrate these tools into your workflow in a practical, hands‑on way. With offices in New York, Paris, London, and Milan, we’re a diverse team united by a bias for action. We ship fast, learn from experiments, and tackle problems that matter: protecting billions in payments for companies worldwide. If you want to see your work make an immediate impact in financial security, Trustpair is built for you. Learn more about how we use AI in everyday work here.

About The Role

Integrated into our talented Engineering Team, you’ll work within one of our feature squads on creating a scalable and efficient product which consistently meets the needs of our clients. You’ll work on collaborative topics such as designing new features & functionalities, implementation, development and even testing the application. Trustpair’s engineering team works with the latest technologies, as a Cellular Organization, meaning we reshape and adapt to ensure our teams stay autonomous, independent and have impact on the decisions made. This is a freelance contract, open to candidates based in the EU.

What You'll Do

• Take the lead in creating innovative features by following best practices and maintaining exceptional code quality
• Engage in every phase of the SDLC; contribute to the architecture, code development, and even oversee the launch of new releases
• Support critical services for our customers which ensures the security of their payments
• Keep a finger on the pulse of the technology landscape. Identify emerging technologies and industry trends, and be proactive in recommending relevant improvements to our existing stack
• Champion engineering excellence by fostering a culture of continuous improvement. Lead by example in practices such as code reviews, Test-Driven Development (TDD), pair programming, writing clean and maintainable code, etc

What's in it for you

• High-Impact in a High-Growth Environment: Join a company with 50% business growth, where tech is one of the core accelerators. You'll be building solutions for a platform with rapidly increasing usage, directly influencing our success.
• Shape Our Future: We want your voice in making the critical architectural, product, and organizational decisions that will define our future.
• Modern Stack & AI-Powered Engineering: Work with a clean Ruby on Rails stack, state-of-the-art DevOps, and managed tech debt. We are aggressively adopting AI, both in our product (LLMs) and to boost your own efficiency with tools like Cursor.
• Culture of Full-Fledged Engineering Ownership: We don't see you as just a developer. You are an engineer with a strong voice and full accountability. We empower you to drive initiatives from technical design to final impact.
• Accelerated Career Growth: Our rapid expansion creates constant and significant opportunities for career advancement, skill development, and taking on new leadership responsibilities.
• Collaborative & International Team: Thrive in a diverse, cross-functional, and international environment. We leverage collective intelligence and a supportive, senior team to solve cutting‑edge challenges.

Must-Haves

• 5 years of experience in Ruby (Rails) back end development
• Ability to conceive the technical design of a complex product feature
• Experience on working on a rapidly growing product; knowledge of architectural models of large scale web applications
• Experience working in an Agile environment like Scrum or Kanban
• Experience in API development and knowledge of resilience, scalability and security constraints
• Fluent in English
• Desire to work on longer term technical challenges & accomplish them

Nice-to-Haves

• Experience in full stack development (React, Javascript, Typescript...)
• DevOps culture, ability to work on deployment pipelines and CI/CD tools like but not limited to: Docker, AWS, GitLab CI
• Experience in an environment where security is important; sensitivity to good security practices
• Experience in mentoring and leadership of junior and experienced people for good practices of software craftsmanship
• Experience with other technologies in high-throughput environments

Recruitment process

• First call with Aicha, Talent Acquisition Manager (30 mins)
• Experience interview with an Engineering Manager (1h)
• Case study with our Tech Lead & an Engineer from our team (1h30)
• Coffee fit with a Product Manager & an Engineer (30 mins)
• Cofounders interview with Alexandre, our MD (45 mins)

Equal Opportunity Statement

Trustpair's policy is to provide equal employment opportunity in all of our employment practices without regard to race, color, religion, sex, national origin, ancestry, marital status, protected veteran status, age, individuals with disabilities, sexual orientation or gender identity or expression or any other legally protected category. Applicants for all positions in Trustpair must be legally authorized to work in the country which they are applying for or be a citizen from Schengen / EU zone. The verification of employment eligibility will be required as a condition of hire.

Additional Information

• Contract Type: Freelance
• Location: Paris
• Unknown