Senior Backend Engineer

The French Sourcer; Paris; Hybrid; EUR 70,000 - 110,000; Full time

Job summary

The French Sourcer in Paris is seeking a Senior Backend Engineer to design and implement scalable backend services for a high-traffic SaaS platform. Hybrid work with onsite in Paris. You will transform a monolith into independent services, optimize APIs, and work with product managers and frontend engineers.

Strong experience with Java/Kotlin/C#/Node.js and relational databases is required. This role emphasizes reliability, performance, and observability, with a focus on architecture decisions

Qualifications

• 5+ years of experience developing backend applications.
• Strong experience with Java, Kotlin, C#, or Node.js.
• Experience designing and maintaining production APIs.
• Good knowledge of relational databases and data modelling.
• Understanding of distributed systems and asynchronous communication.

Responsibilities

• Designing and developing backend services for a high-traffic SaaS platform
• Building APIs used by customer-facing products and internal systems
• Breaking down parts of an existing monolith into clearly defined services
• Improving application performance, reliability, and scalability
• Designing relational data models and optimising critical queries
• Writing automated unit, integration, and API tests
• Reviewing code and contributing to shared engineering standards
• Investigating production issues across applications, databases, and infrastructure
• Working with product managers and frontend engineers to define technical solutions
• Improving deployment and release processes with the platform team
• Contributing to architecture decisions and technical documentation

Skills

5+ years experience

Java

Kotlin

C#

Node.js

Job description

Build the services behind a product used every day, while helping the platform scale beyond its original architecture.

Senior Backend Engineer - Paris

Paris, France · Permanent · Hybrid

What you'd actually work on

• Designing and developing backend services for a high-traffic SaaS platform
• Building APIs used by customer-facing products and internal systems
• Breaking down parts of an existing monolith into clearly defined services
• Improving application performance, reliability, and scalability
• Designing relational data models and optimising critical queries
• Writing automated unit, integration, and API tests
• Reviewing code and contributing to shared engineering standards
• Investigating production issues across applications, databases, and infrastructure
• Working with product managers and frontend engineers to define technical solutions
• Improving deployment and release processes with the platform team
• Contributing to architecture decisions and technical documentation

Where it gets technically interesting

• Evolving a mature platform without interrupting ongoing product delivery
• Deciding which components should become independent services and which should remain together
• Managing data consistency and dependencies across distributed services
• Improving performance on endpoints operating under sustained production load
• Introducing stronger testing and observability into critical legacy components
• Balancing immediate product needs with longer-term architectural improvements

What we're looking for

• 5+ years of experience developing backend applications
• Strong experience with Java, Kotlin, C#, Node.js, or a comparable backend technology
• Experience designing and maintaining production APIs
• Good knowledge of relational databases and data modelling
• Understanding of distributed systems and asynchronous communication