Hybrid Senior Backend Engineer, IAM and Billing

at Langfuse

• Job title: Senior Backend Engineer, IAM and Billing
• Job type: Full Time
• Experience level: Senior
• Salary: €90,000 - €160,000 per year
• Degree requirement: Bachelor's Degree
• Tech skills: Open Source, SQL, TypeScript
• Location requirements: Hybrid, Berlin, Germany

About the role

• (Senior) Backend Engineer responsible for designing IAM and billing systems at Langfuse, enabling secure and reliable platform functionalities. Join our engineering team to support enterprise-level demands.

Responsibilities

• Own authentication and identity: You'll build and evolve how users and API keys authenticate with Langfuse — supporting SSO/SAML, OAuth, API key management, and session handling. You'll make sure auth is secure, fast, and frictionless for teams of every size.
• Design fine-grained authorization: You'll architect the permission model that lets enterprises manage complex organizational structures — projects, roles, and scoped access controls. You'll build the RBAC (and eventually ABAC) layer that product engineers rely on when shipping every new feature.
• Build usage-based billing infrastructure: Langfuse bills based on trace volume. You'll own the metering pipeline that counts events accurately at massive scale, integrates with payment providers, and generates invoices that customers trust. You'll handle plan management, entitlements, and the self-serve upgrade flows.
• Create shared platform APIs: Auth and billing touch every surface of the product. You'll design clean, well-documented internal APIs and abstractions that let product engineers move fast without worrying about permission checks or billing edge cases.
• Support self-hosted flexibility: Many teams run Langfuse on their own infrastructure with their own identity providers. You'll make sure our auth layer integrates cleanly with enterprise identity stacks (LDAP, OIDC, SAML).
• Scale for enterprise adoption: As more large organizations adopt Langfuse, the demands on IAM and billing grow fast — audit logging, compliance requirements, multi-tenant isolation, complex pricing models. You'll be building ahead of that curve.

Requirements

• Strong backend engineer who gets excited about designing secure, reliable platform systems that other engineers build on top of
• Experience building authentication and authorization systems — SSO/SAML, OAuth, RBAC, API key management
• Familiarity with billing or payments infrastructure — usage-based metering, payment provider integrations (Stripe or similar), entitlements
• You think carefully about security, edge cases, and failure modes — especially in multi-tenant environments
• You organize yourself. You have strong opinions about API design, system boundaries, and how to ship shared infrastructure safely
• Comfortable reading and writing TypeScript (our backend) and SQL
• Interest in open source software and empathy for self-hosted operators who need to integrate with their own identity stacks
• Thrives in a small, accountable team where your output is visible and matters
• CS or quantitative degree preferred
• Bonus points:
• Experience building multi-tenant SaaS platforms with enterprise identity requirements
• Background in usage-based billing systems or fintech infrastructure
• Familiarity with compliance frameworks (SOC 2, GDPR) as they relate to auth and data access
• Former founder

Benefits

• Equity