Senior/Staff Kotlin Desktop Engineer

Ersilia; Kraków; On-site; PLN 180,000 - 280,000; Full time

Benefits offered by this job

Private healthcare

MyBenefit points

Language lessons

Training package

In-house training

Home office reimbursement

Flexible hybrid work model

Job summary

Ersilia in Kraków is seeking a senior engineer to join a startup-like consultancy building a desktop control plane for local AI inference. You will work with Kotlin and Compose Desktop to deploy, configure, and manage AI models on local devices, including hardware such as NVIDIA Spark / DGX Spark.

You will own features end-to-end with minimal bureaucracy, shipping quickly in a small, tooling‑oriented team. Fluent English and strong Kotlin/build systems experience are required.

Qualifications

• Strong Kotlin skills and experience with build systems.
• Experience with developer tooling and async/concurrent programming.
• Fluent English.
• Cross-platform desktop development experience.
• Ability to own features end-to-end in a startup-like team.
• Familiarity with REST APIs integration.

Responsibilities

• Build the UI in Compose Desktop for model lifecycle management.
• Integrate with backend REST APIs for deployment and management.
• Set up agent configurations using TOML/JSON/YAML.
• Connect coding agents to locally hosted models.
• Create native installers for Windows, Linux, and macOS.

Skills

Kotlin

Compose Desktop

REST APIs

Kotlin Coroutines

Cross-platform development

Tools

Gradle

Make

Bazel

Job description

Client Information

A leading European software consulting and engineering company, home to 350+ EU-based professionals. Strong engineering culture built on ownership, clean code, and transparency.

Required Skills

Kotlin. Compose Desktop, REST APIs. Kotlin Coroutines. Cross-platform development

Requirements

• Strong Kotlin skills
• Experience with build systems (Gradle, Make, Bazel)
• Experience with developer tooling
• Async/concurrent programming experience
• Fluent English

Job Description

Develop a desktop control plane for local AI inference using Kotlin and Compose Desktop, managing AI models on local devices, with high ownership and fast iteration.

About the role

Join a small, startup-like team building a desktop control plane for local AI inference. You'll work with Kotlin and Compose Desktop to develop an application that deploys, configures, and manages AI models on local devices — including hardware like NVIDIA Spark / DGX Spark. The team has an internal MVP, is in direct contact with potential users, and is moving fast toward open sourcing the tool. There's no bureaucracy: you'll own features end-to-end and your decisions will ship quickly.

This is a role for someone who enjoys working on problems that don't have Stack Overflow answers — where the solution requires original thinking, navigating OS-specific quirks, or designing something that simply hasn't been done in quite this way before.

What you'll work on

Build the UI in Compose Desktop — model lifecycle management, agent configuration dashboards, system load visualization

Integrate with backend REST APIs for model deployment and management

Set up agent configurations using TOML / JSON / YAML and implement LLM proxy routing

Connect coding agents (Claude Code, Codex) to locally hosted models

Create native installers for Windows (MSI), Linux (DEB), and macOS (DMG)

Tech stack

Kotlin, Compose Desktop, kotlinx.coroutines, REST APIs, TOML / JSON / YAML, native packaging (MSI, DEB, DMG). Nice to have: mitmproxy, LiteLLM / OpenRouter-style proxy layers.

What we're looking for

Strong Kotlin skills are the foundation, but we care just as much about how you think and work.

Build systems depth — You've not just used tools like Gradle, Make, or Bazel, but developed and maintained build systems. You've wrestled with a genuinely hard build problem and came out the other side with something you're proud of.

Developer tooling instinct — Experience building or maintaining tools for developers: IDE plugins, CI/CD tooling, internal workflow automation, review tooling, or similar. If you've contributed to open source or worked on DX-focused projects, we'd love to hear about them.

Async / concurrent programming — Solid command of Kotlin Coroutines and the reasoning skills to use them correctly under real-world conditions.

Cross-platform awareness — Practical understanding of how Windows, macOS, and Linux differ at the level that matters for desktop apps.

Technical depth preference — You gravitate toward low-level, in-the-weeds technical work. You're comfortable with architectural decisions but happiest when building.

Independent and collaborative — You can drive a feature solo, but you value code review and close collaboration with a small team.

Fluent English

Benefits

Private healthcare, MyBenefit points, language lessons, training package, in-house training, home office reimbursement, flexible hybrid work model.

Briefing Notes

Mission & Context

PE-backed software consultancy, is building a desktop control plane for local AI inference in a small, startup-like team. This role exists to accelerate the development of their MVP, which manages AI models on local devices, with the goal of open-sourcing the tool. The project is fast-paced, with high ownership and minimal bureaucracy, moving from an internal MVP to a public release.

Candidate Overview

The ideal candidate is a senior engineer with deep, hands‑on experience in Kotlin. They must have a strong background in building or maintaining developer tooling and complex build systems like Gradle, Make, or Bazel. Proficiency in asynchronous and concurrent programming, specifically with Kotlin Coroutines, is non‑negotiable. This role requires practical experience developing cross‑platform desktop applications and a mindset geared towards solving low‑level technical problems independently.

Green Flags

• Experience building and shipping developer‑focused tools (e.g., IDE plugins, CI/CD tooling, workflow automation).
• Active contributions to open‑source projects, especially in the tooling or infrastructure space.
• Proven experience shipping a 0-to-1 product in a small team or startup environment.
• Background at companies known for strong engineering and tooling culture, such as JetBrains.
• Demonstrated ability to own features end-to-end with high autonomy.

Red Flags

• Career spent exclusively in large, highly‑structured corporate environments (e.g., Allegro).
• Profile shows only web or mobile development with no desktop, systems‑level, or tooling experience.
• Primary experience is in management, not hands‑on, in‑the‑weeds engineering.
• Requires significant supervision or is not comfortable with ambiguity and independent problem-solving.
• Not located in Poland or a nearby European time zone.
• Unwilling to work on a B2B contract basis.
• Not fluent in English.

Internal Context

Hiring Manager is Head of Scala & Tooling. He prioritizes quality over quantity and is focused on finding someone with a tooling-first mindset. Avoid candidates from large, structured companies like Allegro where individual ownership is limited. The budget is competitive for the Polish market but cannot compete with top‑tier international startups. The team has a low organic hiring success rate (~35%) due to the niche nature of the role, so proactive sourcing is critical.

Vibe Check

The team has a 'no bureaucracy' startup vibe within a larger consultancy. The hiring manager values deep technical expertise and a 'client attitude' even for internal projects. The ideal candidate is someone who prefers being 'in the weeds' and building things over high‑level architecture or management, and who thrives on autonomy and solving novel problems.

Nice-to-Haves

• Experience with IntelliJ plugin development.
• Familiarity with Scala.
• Experience with AI/LLM proxy layers (e.g., LiteLLM, OpenRouter).
• Knowledge of network proxy tools like mitmproxy.
• Experience integrating with coding agents like Claude Code or Codex.

Soft Skills

• High sense of ownership ('Sprawczość') and autonomy.
• Problem‑solving mindset; enjoys challenges without clear solutions.
• Ability to work independently for extended periods.
• Strong communication skills for collaborating in a small team and with users.
• Pragmatic and comfortable with a 'learning on the go' mentality.

Ideal Companies

• Software Mansion SA
• Miquido Spólka Z Ograniczona Odpowiednoscia
• AVSystem Slawomir Wolf SpJ
• Ardigen SA
• Schibsted Tech Polska Sp zoo
• J-Labs Software
• 33 Grand Parade Ltd.
• Ailleron SA
• Sabre Poland
• DreamLab Sp zoo

Interview Process

1. Initial Screen (30 mins): Behavioral assessment with a Talent Partner .

2. Technical Interview: Live coding/problem-solving session with a technical recruiter.

3. Business & Hiring Manager Interview (1 hour): Discussion with hiring manager focusing on tooling, client attitude, and technical depth.

Visa & Work Authorization

This is a remote role, but candidates must be based in Poland or a 'reasonable part of Europe' (similar time zone). Candidates must have existing work authorization for their country of residence. The company does not appear to offer visa sponsorship for this position.

Form of Employment

Full-time, B2B Contract