Senior Fullstack Engineer: Build Production-Grade Web & APIs

Reaktor; Helsinki; Hybrid; EUR 90,000 - 120,000; Full time

Job summary

Reaktor is seeking a Senior Fullstack Developer to join one of our Business Units in Helsinki, Finland. You’ll work across modern web applications, backend services and production systems, solving ambiguous problems with clients and thriving in a low‑hierarchy environment.

You will collaborate with clients across digital product, platform and service domains, contributing to architecture, tooling and delivery while maintaining production quality in diverse projects and teams.

Qualifications

• Strong experience in modern frontend development (TypeScript, React).
• Strong experience in backend service development (Node.js, Java, Kotlin, Python).
• Proven track record of building production‑grade digital products.
• Experience across full delivery lifecycle: implementation to production quality.
• Understanding of cloud environments, CI/CD and deployments.
• Ability to work directly with clients in a senior, consultative role.
• Hands‑on mindset with ability to move projects forward.
• Fluent English in an international environment.

Responsibilities

• Build and improve modern web applications, backend services, APIs and data models.
• Work across frontend, backend and infrastructure based on client needs.
• Help clients choose technologies, architecture and delivery approaches.
• Contribute to cloud environments, CI/CD pipelines, deployments and production quality.
• Debug, test, monitor and improve production systems.
• Collaborate with client tech teams and stakeholders.
• Clarify ambiguous requirements and turn them into working software.
• Take responsibility for delivery and support the team.
• Leverage AI‑assisted development tools where appropriate.

Skills

TypeScript

React

Node.js

Java

Kotlin

CI/CD

Cloud platforms

Job description

Reaktor is seeking a Senior Fullstack Developer to join one of our Business Units in Helsinki, Finland. You’ll work across modern web applications, backend services and production systems, solving ambiguous problems with clients and thriving in a low‑hierarchy environment.

You will collaborate with clients across digital product, platform and service domains, contributing to architecture, tooling and delivery while maintaining production quality in diverse projects and teams.