Software Engineer - Defence & Security

Reaktor’s tech community is looking for an experienced Software Engineer to join our specialized Defense & Security Business Unit in Helsinki.

If you are comfortable working across modern web applications, backend services and production systems, enjoy solving complex, high-stakes problems with clients, and are curious to work in a low-hierarchy environment, you might just be what we’re looking for.

You will support clients across a range of digital product, platform, and secure service domains. The exact client context may vary from focused, agile product teams to large defense contractors and national security organizations working on mission-critical and resilient systems.

Your Daily Tasks May Include:

• Building and improving modern web applications, backend services, APIs and data models.
• Working across frontend, backend and infrastructure depending on the needs of the client project.
• Helping clients choose suitable technologies, architecture, and secure delivery approaches.
• Debugging, testing, monitoring and improving production‑grade systems.
• Contributing to private cloud/ on-prem environments, CI/CD pipelines, automated testing, and high‑availability production quality.
• Collaborating directly with client tech teams, designers, domain experts, business stakeholders and other disciplines.
• Clarifying ambiguous requirements and turning them into working software.
• Taking responsibility for delivery while making sure the team is supported and no one is left behind.

To Thrive in This Position, You’ll Need:

Must-haves:

• Strong experience in backend service development, for example with Node.js, Java, Kotlin, Scala, Rust, Python or comparable technologies.
• Experience building, shipping, and improving production‑grade digital products with a strong emphasis on security, data integrity, and reliability.
• Comfortable working across the full delivery lifecycle, from implementation to testing, deployment and production monitoring.
• Understanding of cloud‑native or hybrid environments, CI/CD and secure deployments.
• Know‑how on databases (e.g. PostgreSQL).
• Ability to work directly with clients, domain experts, and other stakeholders in a consultative role.
• Strong problem‑solving skills and the ability to bring clarity to unclear situations.
• A hands‑on mindset — you are technically credible, actively contribute to the work, and help the team move forward.
• Eligibility for a Finnish Security Clearance due to client and security regulations (Suojelupoliisin turvallisuusselvitys). This requires Finnish citizenship.
• Fluency in both Finnish and English (written & spoken).

Nice-to-haves:

• Experience in regulated or mission‑critical environments.
• Familiarity with on‑prem environments, comfortable with Linux.
• Familiarity in infrastructure‑as‑code (IaC), containerization (Kubernetes), or DevSecOps practices.

Workplace type:

• Willingness to work onsite at the office. (Depending on the project’s security classification, some of the projects may require very strict on‑site presence).

While working at Reaktor, we’ll provide you with:

• The ability to impact how you work. Together with the client, your team chooses the approach, technologies, and methodologies you think will work best in any given situation.
• A community with as much support as your heart desires.
• A team that’s not only experienced but considerate as well – they all want you to succeed.
• A sustainable work‑life balance and support for your daily life outside of work. (e.g. free moving day, Reaktor car share, sick child care services, office space to use for your private events, etc.).
• An opportunity to grow as a professional. In addition to the day‑to‑day work, we offer internal training courses, community events, and other opportunities to discuss hot topics in tech and AI.
• Many different hobby clubs, from winter swimming and running to knitting and archery, that bring people together outside of (and sometimes inside) office hours. Many of these are supported by Reaktor.
• Check more benefits and perks below.

Benefits

Tools

We offer everyone a top‑spec computer and a phone of their choosing to work with and use at work and home. If you need other tools, like a keyboard or a mouse, we’ll figure it out, too!

Phone & internet

To keep you connected, we’ll cover an unlimited phone plan – and a proper internet connection to your home.

We offer the monthly lunch benefit in addition to your salary, which means you only pay the taxes.

Recreational benefit (sports & culture)

At Reaktor, the recreational benefit is an addition to your salary – and it’s tax‑free.

Family support

We support all types of families with encouraging types of parental leave and more, offering support for child care.

Extensive insurance package

Our extensive insurance package safeguards you for accidents, travel, and more.

Our subsidized massage deals keep those shoulders nice and loose.

Extensive occupational healthcare

Extensive occupational health care services include specialists’ appointments, operations, vaccinations, dental care, and mental health services, including e.g. psychotherapy.

The Juice‑program enables you to work on open source projects – and get compensated for it!

We’re an equal opportunity employer

All applicants will be considered for employment without attention to race, color, religion, sex, sexual orientation, gender identity, national origin, veteran or disability status.