Senior Fullstack Developer

About the Position

Reaktor's tech community is looking for an experienced Senior Fullstack Developer to join one of our Business Units in Helsinki.

If you are comfortable working across modern web applications, backend services, and production systems, enjoy solving ambiguous 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 service domains. The exact client context may vary from focused product teams to large international companies working on high-traffic, business-critical services.

Many of our clients are technically mature and expect a high level of expertise from our consultants. This means you will need to be hands-on, pragmatic, and comfortable helping both the client and the team make good technical decisions.

Responsibilities

• 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 delivery approaches
• Contributing to cloud environments, CI/CD pipelines, deployments, and production quality
• Debugging, testing, monitoring, and improving production-grade systems
• Working on products or tooling related to customer-facing services, internal platforms, identity, martech, customer support, analytics, online stores, integrations, developer tooling, or SDKs
• Collaborating directly with client tech teams, business stakeholders, designers, product people, 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
• Using modern development practices, including openness to AI-assisted development tools and workflows

Requirements

• Strong experience in modern frontend development, for example with TypeScript, React, or comparable technologies
• Strong experience in backend service development, for example with Node.js, Java, Kotlin, Scala, Clojure, Python, or comparable technologies
• Experience building, shipping, and improving production-grade digital products
• Comfortable working across the full delivery lifecycle, from implementation to testing, deployment, and production quality
• Understanding of cloud environments, CI/CD, deployments, and how production systems are operated
• Ability to work directly with clients, stakeholders, and other disciplines in a senior, consultative role
• Strong problem-solving skills and the ability to bring clarity to ambiguous product or technical situations
• A hands-on mindset - you are technically credible, actively contribute to the work, and help the team move forward
• Fluent verbal and written English skills to collaborate in an international environment

Nice to Have

• Experience from customer-facing digital products, online services, ecommerce, subscriptions, internal platforms, analytics, martech, or similar product domains
• Experience with high-traffic or business-critical production systems
• Deeper experience with platform engineering, infrastructure-as-code, or DevOps practices
• Experience with customer-facing products, internal tools, integrations, SDKs, or developer tooling
• Familiarity with mobile development or React Native
• Finnish language skills

We Offer

• Opportunity to work in a hybrid setup, balancing office, client premises, and remote work depending on the client project and team needs

About the Company

Reaktor is a leading tech community in Finland, providing innovative solutions and services to clients across various industries. We value a low-hierarchy environment, continuous learning, and professional growth.