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voize is building AI companions that automate digital workflows for frontline workers, backed by $50M Series A funding from Balderton Capital, Y Combinator, and others. The company serves 2,000+ facilities with 200,000+ active users.
As Senior Backend Engineer on the Agent SDK team, you will own the Kotlin-based runtime foundation that powers voize's AI agents across verticals and markets. This is a permanent, high-leverage role where your work directly reduces the cost and complexity of deploying additional agents.
Key responsibilities include:
- Building and maintaining the SDK as an internal product, shaping the runtime and client-facing contracts that consuming teams depend on. You help set the SDK's roadmap and own its evolution.
- Designing and shipping the identity and authentication layer that enables agents to operate with real user context and permissions.
- Implementing comprehensive observability by default: wiring telemetry, error reporting, inference tracking, and anonymization into the SDK so every consumer benefits automatically.
- Creating the testing infrastructure and architecture tests that protect runtime internals and establish evaluation gates before model changes ship.
- Managing ecosystem evolution on behalf of consuming teams: owning Kotlin version upgrades, format compatibility, and shared limits on tool output and token usage so changes propagate once from the SDK to all downstream teams.
You bring several years of production backend experience in Kotlin, ideally with exposure to SDKs or internal platforms where your published contracts are the product. You have hands-on experience with testing, observability tooling, and making codebases comfortable for other engineers. You are drawn to AI agent systems and understand the orchestration and evaluation challenges in the space. You communicate clearly, gather requirements from cross-functional teams, and bring others along on technical decisions.
voize offers a hybrid setup based in Berlin with flexibility to work remotely across Germany. Benefits include 30 vacation days plus birthday off, Germany Transport Ticket, Urban Sports Club membership, stock options, learning platform access, free language courses, and flexible working hours. The role offers rapid growth, real impact, and the opportunity to help frontline workers reclaim time for meaningful work.
