Senior Software Engineer Java & Kotlin

hyperexponential; Wysokie Mazowieckie; Hybrid; PLN 180,000 - 240,000; Full time

Job summary

A leading AI company is seeking a Senior Engineer to help build and improve their product hx Renew. This hybrid position requires strong skills in Kotlin, with responsibilities including system development, architectural work, and community engagement. The role offers competitive salary and benefits in a collaborative environment.

Benefits

Share Options

25 days of non-working days

Mental Health Support

Top-spec laptop

Company Sick Pay

Qualifications

• Experience with Kotlin or any JVM language.
• Willingness to work on architectural modularization.
• Focus on delivering high-quality, well-structured code.

Responsibilities

• Work with product managers, designers, and fellow engineers to develop solutions.
• Promote hx in the community via open source contributions.
• Join an on-call rota for production support.

Skills

Kotlin

Spring

Hibernate

Job description

Location: Hybrid 2 days per week, based in Warsaw

Salary for Senior (IC3)

• UoP (Contract of Employment) = 23,000 - 31,000 PLN per month gross

About hyperexponential (hx)

At hyperexponential, we’re building the AI-powered platform that enables the world’s most critical decisions in a $7 trillion industry, which risks to take, and how to price them. These are the decisions that shape real‑world outcomes: whether rockets successfully launch into space, autonomous vehicles make it to market, or communities recover after major storms.

Until now, insurers have been making billion‑dollar decisions using outdated tools. We’re changing that. Our platform brings together data, AI, and human expertise to give insurers the fastest path from submission to decision - helping them move faster, act smarter, and take on more risk with confidence.

Backed by a16z, Highland Europe, and Battery Ventures, we’re scaling globally - already trusted by nearly 50 of the world’s largest insurers, with zero churn and billions in premiums flowing through hx.

What began as a single product in one market has rapidly evolved into a multi‑product, multi‑territory platform powering every stage of pricing and underwriting. AI is at the core of what we do - from building the world’s first domain‑specific AI peer programmer for insurance (think GitHub Copilot with a PhD in actuarial science) to shaping agentic workflows that reinvent how this industry operates.

What makes hx different is the people who build it. Here, impact isn’t tied to title or tenure; it’s defined by the challenges you take on and the discipline you bring.

Surrounded by peers who stretch you, you’ll do the best, hardest work of your life in a company engineered to endure.

If that sounds like you, join us in building what comes next.

About Your Role

The Policies Team works at the heart of our product hx Renew, building a system that keeps track of all our customers’ models, policies and much more! Sounds like a boring CRUD? We have domain logic and invariants to show for, and to keep track of. Your mission, should you choose to accept it, will be to join us on the journey of chopping the monolith, introducing DDD and hexagonal architecture to our code, all while delivering brand new workflows and features.

• Help us build the right thing by working with product managers, designers, fellow engineers, and (sometimes) customers to understand problems and develop solutions
• Help us build the right thing by writing high‑quality, thoughtful, simple, commented, documented, tested, well‑structured code aligned to our constants, principles and standards
• Help drive our technical standards, decisions, and strategy
• Continually learn and improve yourself - experiment and play with new technologies through your work and hackathons
• Help reduce friction and eliminate impediments that slow us down
• Promote hx in the community by contributing to open source projects, writing blog posts and/or presenting at virtual meetups/conferences
• Help support our product in production by joining an on‑call rota

What You Need To Be Successful

• The majority of our work lies with Kotlin, Spring & Hibernate, so experience with Kotlin would be best, but any JVM language will be highly relevant as well.
  • You will be upskilled in Kotlin if you haven’t already used it!
• We will focus on deeper architectural work, like modularising our monolith and isolating technical solutions like authentication and authorisation.
• Additionally, we are conducting product work on new features, expanding our product coverage.

Interview Process

• Initial screening with Talent team to kick things off (30 minutes)
• Technical Assessment (120 minutes)
• Values Interview (60 minutes)
• We offer!

How hx Warsaw Works

At hyperexponential, we believe in a balance between remote work, and building relationships across teams and locations. You’ll have your main office in Warsaw, 2 days a week, with also ability to travel to London HQ to meet the wider team. International travel will be much less frequent, perhaps 2-3 times a year.

Warsaw HQ was established in 2023, quickly hiring our first handful of high‑calibre engineers. Fast‑forward to today in 2025, there are 50+ in Warsaw and surrounding cities who travel for the collaborative environment.

On Wednesdays you’ll often find Warsaw HQ organising team lunch paid by hx, getting drinks after hours. The office is also dog‑friendly, so feel free to bring yours along!

What Your Offer Could Look Like

B2B

• Share Options at a highly successful Series B company
• 25 days of non‑working + Polish bank holidays
• Mental Health Support and Therapy via Spectrum Life
• Optional for you: access to Private Healthcare via Luxmed + Multisport (fully funded by yourself as B2B Contractor)
• Top‑spec laptop (MacOS or Windows)

Contract of Employment (UoP)

• Share Options at a highly successful Series B company
• 26 days of holiday + Polish bank holidays
• Company pension
• Company Sick Pay for 10 days at 100% salary
• Mental Health Support and Therapy via Spectrum Life
• Monthly Wellbeing allowance via Juno
• Private Healthcare Insurance via Luxmed
• Multisport - Classic level
• Top‑spec work equipment (MacOS, Windows + additional monitors, mechanical keyboards etc)