Senior Backend Engineer - Kotlin (m/f/d) - Agent SDK

About voize

At voize, our core belief is that frontline workers deserve more time to care, interact, and focus on people rather than busywork and cumbersome systems. Our goal is to develop AI companions that seamlessly manage digital workflows, empowering humans instead of replacing them. Supported by a $50M Series A round led by Balderton Capital and participation from HV Capital, Y Combinator, and other prominent investors, voize currently supports over 2,000 facilities and 200,000 users who rely on our AI tools to simplify their workloads.

Your Role

As a Senior Backend Engineer focused on our Agent SDK, you will develop and maintain the Kotlin-based platform that powers our AI agents. This SDK serves as the foundation across various verticals and markets and requires a dedicated owner to enhance performance and cost-efficiency for subsequent agents. Your efforts will directly support feature teams by providing a robust layer that reduces incremental costs for additional agents.

Key Responsibilities

• Develop and sustain the SDK as an internal product, shaping runtime components and defining client-facing contracts that enable seamless integration for consumer teams.
• Create and manage the identity framework for agents, enabling user-authenticated interactions. Depending on the existing infrastructure, you may design and implement authentication mechanisms.
• Ensure all agents launched through the SDK offer comprehensive observability by integrating telemetry, error reporting, inference, and data anonymization built in by default.
• Design and build the necessary testing framework and architectural tests to maintain SDK runtime integrity. Coordinate with the ML team to run SDK agents through evaluation harnesses prior to model deployment.
• Manage ecosystem transitions such as version updates, format compatibility, and regulating output limits to provide smooth upgrades for all dependent teams.

Qualifications and Skills

• Extensive experience in backend development using Kotlin, particularly in building production-ready internal tools like SDKs or platforms with public-facing contracts, including managing versioning challenges.
• Strong focus on testing and system observability, implementing tools and processes that facilitate maintainability and team collaboration.
• Familiarity or enthusiasm for AI agent technologies, especially orchestration and evaluation systems underpinning these solutions.
• Effective communication skills in English, with an aptitude for gathering requirements and conveying complex reasoning clearly across cross-functional teams.

Company Culture and Benefits

• Join a rapidly scaling startup dealing with meaningful challenges and opportunities to make a tangible impact on frontline workers' lives.
• Experience a transparent and collaborative work environment with regular events either in the Berlin office or remotely across Germany.
• Enjoy potential equity participation through stock options.
• Benefit from attractive perks including 30 days vacation plus birthday off, public transport ticket for Germany, access to Urban Sports Club, company retreats, and subscriptions to learning resources such as Blinkist and Audible, alongside free language classes.
• Flexible scheduling and hybrid work options to accommodate your preferred working style.