Senior Backend Engineer – Kotlin

• Build and maintain the Kotlin Agent SDK as an internal product

• Shape the SDK runtime and client-facing contracts

• Help define the SDK roadmap

• Build the identity layer and authentication plumbing for agents

• Integrate telemetry, error reporting, inference, and anonymization into the SDK

• Create the SDK test kit and architecture tests

• Build integration with the ML team's evaluation harness before model changes ship

• Own Koog version upgrades and format compatibility

• Define shared limits for tool output and token usage

• Support consuming engineering teams by absorbing ecosystem changes

Requirements

• Several years building production backend systems in Kotlin, including systems consumed by other engineers

• Experience building an SDK or internal platform where the published contract is the product

• Experience with versioning work associated with consumed SDKs or platforms

• Experience setting up testing and observability tooling

• Interest and familiarity with AI agent systems, orchestration, and evaluation

• Clear communication in English

• Proficiency in Kotlin and Coroutines

• Excellent fluency in English

• Legal right to work in Germany

• Based in Berlin, willing to relocate to Berlin, or seeking remote work within Germany

• Remote work within Germany requires travel to Berlin every 3 months for work-weeks

Core Competencies

Demonstrates expertise in building and maintaining SDKs, particularly in Kotlin, with a focus on backend systems and integration of observability tooling. Proficient in defining product contracts and managing versioning for internal platforms.

Highest-signal resume keywords

• Kotlin Development

• SDK Development

• Versioning Management

• Testing and Observability Tooling

• AI Agent Systems Familiarity

Hard Skills

• Kotlin

• Coroutines

• Backend Systems Development

• SDK Architecture

• Integration Testing

• Telemetry Integration

• Error Reporting

• Anonymization Techniques

• Version Control

• Contract Definition

Soft Skills

• Clear Communication

Industry Keywords

• AI Agent Systems

• Orchestration

• Evaluation Harness

• Ecosystem Changes

• Remote Work