Senior Software Engineer

Mambu Payments (formerly Numeral); Paris; On-site; EUR 90,000 - 130,000; Full time

Job summary

Mambu Payments (formerly Numeral) is hiring Senior Backend Software Engineers to build secure, high-performance banking and payments software. You will own architecture for distributed backend systems, mentor engineers, and drive technical roadmaps in a fintech SaaS environment.

Join a high-velocity team focused on scalable APIs, interoperability, and cloud-native deployments to support a growing SaaS platform used across financial services.

Qualifications

• 5+ years of professional software engineering experience, with significant hands-on experience in Golang.
• Background in fintech, banking, or payments, with regulatory understanding.
• Proven track record designing and owning complex distributed backend systems in production.
• Deep experience with relational databases and SQL in high-concurrency environments.
• Advanced API design skills with focus on security, versioning, and documentation.

Responsibilities

• Developing bank connectivity and payment automation products with emphasis on security, stability, and performance.
• Own architectural decisions for complex projects and guide technical direction.
• Collaborate with Product Managers and DevOps Engineers to maintain fast-paced delivery.
• Apply security by design to APIs and internal systems.
• Mentor junior and mid-level engineers through code reviews and pairing.

Skills

Golang

Distributed backend

Relational databases

API design

Security by design

Backend architecture

Mentoring

Tools

GitLab

Kubernetes

Job description

Join the fintech revolution with Mambu, the leading SaaS cloud banking platform. We're on a mission to make banking better for a billion people. We're engineering the future of financial services with AI at its core. At Mambu, AI isn't a feature — it's how we're rebuilding banking from the ground up. If you're ready to apply cutting-edge technology to problems that affect millions of people, your next chapter starts here. Learn more here .

We are hiring Senior Backend Software Engineers across all teams. As a Senior Backend Software Engineer, you will be responsible for:

• Developing bank connectivity and payment automation products, features, and capabilities, with a focus on security, stability, and performance
• Owning architectural decisions for complex, high-impact projects and driving technical direction across teams
• Collaborating with Product Managers and DevOps Software Engineers to maintain a fast-paced, iterative, and continuously improved product development and delivery process
• Applying security by design principles to public and internal APIs
• Solving architectural and technical challenges to reduce complexity while creating value for customers and users
• Mentoring and upskilling junior and mid-level engineers through code reviews, pair programming, and technical guidance
• Defining and executing Numeral's technical roadmap to improve team velocity and control technical debt
• Acting as a technical reference and escalation point for critical incidents and high-stakes production issues.
• 5+ years of professional software engineering experience, with significant hands‑on experience in Golang
• Background in fintech, banking, or payments (SEPA, Swift, Ebics…), with an understanding of the regulatory and operational constraints of the industry
• Proven track record designing and owning complex, distributed backend systems in production
• Deep experience with relational databases and SQL, including high-concurrency environments, transaction management, and isolation levels at scale
• Strong understanding of the challenges of running a high-volume SaaS platform at scale, with a track record of producing quality, maintainable, well-documented code that respects best practices
• Advanced API design skills, with a strong focus on security, versioning, and documentation
• Demonstrated ability to mentor engineers and elevate team-wide engineering standards
• You are curious, interested in business understanding and product oriented
• You are highly autonomous, proactive, and comfortable driving ambiguous technical problems to resolution

Nice-to-have skills

• DevOps appetite - you have been in involved in implementing / using CI using Gitlab and Kubernetes
• Cloud hosting with AWS and experience with EC2, S3, EKS, RDS…
• Familiar with Kafka or similar message broker middlewares