Senior Backend Engineer (Kotlin) — Agent SDK & AI, Remote

voize; Warszawa; Hybrid; PLN 394,000 - 569,000; Full time

Benefits offered by this job

Stock options

30 vacation days

Germany Transport Ticket

Urban Sports Club

Company off-sites

Learning platforms (Blinkist & Audible

Free language courses

Job summary

voize is seeking a Senior Backend Engineer to own the Kotlin foundation behind our AI agents. You will build and maintain the SDK as an internal product, define client-facing contracts, and ensure robust identity, telemetry, and observability from day one.

You will own the SDK's evolution, test strategy, and integration points with our ML evaluation harness. Join a fast-growing startup focused on time-saving AI for frontline workers across Germany.

Qualifications

• Proven backend experience on JVM with Kotlin/Java/Scala.
• Experience designing APIs that other engineers depend on.
• Strong focus on testing and observability across services.

Responsibilities

• Build and maintain the Kotlin-based backend SDK and internal contracts.
• Shape the identity layer and auth plumbing for agents.
• Ensure observability, telemetry, and error reporting are embedded by default.
• Create and maintain the test kit and architecture tests for runtime internals.
• Manage Koog version bumps, format compatibility, and upgrade paths across the SDK.

Skills

Kotlin

Java

Scala

APIs design

Testing

Observability

Job description

voize is seeking a Senior Backend Engineer to own the Kotlin foundation behind our AI agents. You will build and maintain the SDK as an internal product, define client-facing contracts, and ensure robust identity, telemetry, and observability from day one.

You will own the SDK's evolution, test strategy, and integration points with our ML evaluation harness. Join a fast-growing startup focused on time-saving AI for frontline workers across Germany.