Senior Software Engineer (Cybersecurity)

TL;DR

Senior Software Engineer (Cybersecurity): Building and owning security integrations and detection features for customer-side libraries with an accent on .NET and Java. Focus on instrumenting thousands of production applications, managing operational telemetry, and optimizing performance and cost.

Location: Bordeaux, Lyon, Madrid, Nantes, Paris, or Sophia Antipolis

Company

Datadog is a monitoring and security platform that enables engineers to understand and scale their systems, applications, and teams at a massive scale.

What you will do

• Design and build security integrations (WAF, RASP, API Security, IAST, SCA) across multiple libraries, focusing primarily on .NET and Java.
• Develop production-hardened code that safely instruments thousands of applications globally.
• Monitor production telemetry to debug complex cross-system issues and reduce customer-facing problems.
• Shape the technical roadmap by defining OKRs, driving RFCs, and breaking down features for parallel development.
• Collaborate with product management and backend/frontend teams to turn security ideas into adoptable capabilities.
• Mentor teammates and improve overall code quality and testing standards.

Requirements

• Expertise in at least one of .NET (C#) or Java, with a polyglot ability to contribute to other languages.
• Strong software engineering fundamentals with a track record of shipping modular, maintainable code.
• Experience building and shipping SDKs or libraries consumed by other developers, including versioning and compatibility.
• Proven ability to measure and optimize performance and resource costs (time and space).
• Strong communication skills for driving alignment through RFCs and providing constructive peer feedback.
• Degree in STEM or equivalent professional experience.

Nice to have

• Deep knowledge of language runtime internals (JVM bytecode instrumentation, Java agents, or CLR/JIT/GC).
• Background in application security, such as WAF, RASP, SAST/IAST/SCA, or threat detection.
• Experience with auto-instrumentation, APM, or distributed tracing.
• History of maintaining open-source projects and publishing packages (e.g., NuGet, Maven).
• Experience with AI-assisted developer tooling or agentic workflows.

Culture & Benefits

• Engineering culture based on pragmatism, honesty, and simplicity.
• Opportunity to work on high-scale systems processing trillions of data points daily.
• Collaborative environment focusing on solving hard problems the right way.