Senior Software Engineer

Description de l’emploi Le contenu du poste est libellé en anglais car il nécessite de nombreuses interactions avec nos filiales à l’international, l’anglais étant la langue de travail. This job offer is accessible to all, regardless of gender. Job title: Senior Software Engineer Location: Paris - Hybrid (3 days a week onsite, 2 days work from home) About the job Sanofi is building a GenAI platform that helps product and business teams move from isolated AI experiments to secure, reusable, production-ready capabilities. In a nutshell, a platform team creates the foundational layers and core building blocks that other teams rely on. We do not always provide direct business value ourselves; we help other technical teams focus on their own products by reducing repeated work, defining shared patterns, and building reusable capabilities. Our platform covers several layers: Cloud-native building blocks, infrastructure, and deployment patterns APIs, SDKs, shared libraries, and internal tools Observability, security, access control, and operational standards Document ingestion, knowledge retrieval, and GenAI data pipelines Agent creation, agent orchestration, evaluation, and governance capabilities GenAI and agentic capabilities are a growing part of that mission. As highlighted in the AWS Sanofi success story, Concierge has evolved into a unified, agentic AI companion used across the company. The GenAI Platform team builds the foundations that make this kind of experience possible: reusable agent patterns, secure APIs, knowledge pipelines, evaluation frameworks, and governed orchestration layers. One key project you will contribute to is AgentsHub , the central platform through which AI agents are registered, discovered, governed, and invoked. AgentsHub is designed to become the high-scale traffic layer between Sanofi applications, such as Concierge, and specialized agents that perform data retrieval, workflow automation, and system write-back. What You Will Build You will contribute to platform products built with TypeScript, Node.js, React, AWS services, Terraform, and modern GenAI integration patterns. The role is hands-on and product-oriented. Depending on priorities, you may work on backend APIs, internal UIs, cloud infrastructure, shared libraries, automation tooling, agent registries, knowledge integrations, evaluation capabilities, or operational dashboards. This is not a classical feature-team role where the scope is limited to one business application. You will work on foundational platform capabilities that enable many teams to move faster and build safer, more reliable GenAI products. Job Description Your key responsibilities will be Build and evolve reusable backend platform capabilities for GenAI applications, AI agents, knowledge retrieval, and cloud-native services Design and implement APIs, shared libraries, and automation workflows used by other engineering teams, including internal UIs and back-office tools for managing platform resources and agents Improve the reliability, security, observability, and scalability of platform services on AWS, integrating with GenAI building blocks such as Bedrock, Bedrock AgentCore, vector databases, knowledge bases, and agent interoperability protocols Contribute to production-readiness patterns: RBAC, audit logs, health checks, versioning, metrics, and operational tooling Collaborate with squads and product teams to turn repeated needs into reusable platform primitives, and document and advocate for platform capabilities across Sanofi What we offer you: A fixed salary over 12 months, supplemented by a short-term incentive, as well as a collective variable compensation based on Sanofi Group results. Because taking care of our employees is also our mission: Benefits & Well-being: Quality health insurance, extended maternity/parental leave (18/14 weeks), enhanced support in case of illness, teleconsultation and second medical opinion covered by Sanofi, as well as many other wellness programs to discover here. Work-Life Balance: 31 days of paid leave + RTT depending on your status, remote work up to 2 days/week Transportation: Public transport coverage up to 80% Savings & Retirement: Group Savings Plan and PERCOL with employer matching, and PERO Professional Development: Internal and international mobility opportunities, learning & development opportunities And more: platforms dedicated to peer-to-peer recognition & service exchanges between Sanofi employees (carpooling, home exchanges, etc.), numerous CSE benefits... About you Key Technical Requirements & Qualifications You do not need to check every point. If you fit only some of them and are eager to learn the rest, that is more than enough. Expect to work on most of these topics during your daily tasks. Strong curiosity for GenAI, LLMs, and AI agents; familiarity with GenAI application patterns (LLM APIs, RAG, tool calling, agent orchestration, MCP, A2A, evaluation, guardrails, vector databases) is a plus Solid backend engineering experience in JavaScript/TypeScript and Node.js (Python is a good second option); experience designing and building APIs, backend services, or distributed systems Experience with AWS or another cloud provider, including serverless/event-driven architectures (Lambda, API Gateway, DynamoDB, SQS, Step Functions, ECS, or equivalents) Understanding of authentication, authorization, RBAC, API security, and enterprise identity patterns Interest in observability, debugging, tracing, logging, and operating production systems Infrastructure as Code experience (Terraform, CDK, or similar) is a plus React or modern frontend experience is a plus English is mandatory as we are an international team Soft and behavioral skills Strong ownership mindset: you care about the product, the users, and the quality of what you ship Comfortable working with multiple teams to drive alignment and results Service-oriented mindset: you enjoy building platforms that help other engineers and product teams succeed Self-motivated, autonomous, and able to make progress in ambiguous situations Pragmatic problem solver with critical thinking and good judgment Clear written and verbal communication skills Positive team player, open to feedback, and willing to share knowledge Comfortable working in a fast-moving environment where patterns are still being invented Your background Several years of experience building software products, backend systems, platform services, or cloud-native applications No specific diploma is required, but a Bachelor’s degree or equivalent experience in Computer Science, Engineering, or a related field is a plus Experience