Senior Developer - Identitetsplattform (CIAM)

Senior Developer Role at Fortnox

We believe in a society shaped by successful companies where entrepreneurship and community benefit go hand in hand. Being part of Fortnox means being part of constant change - a change where you decide how far you want to go. Our biggest focus is to give you the right conditions to live your passion with us. Where you come from is not relevant - where you are headed is interesting to us. Just like we couldn't dream of the Fortnox of today yesterday, you can be part of shaping who we are tomorrow.

Every login, every authorization check, every context switch between companies - all pass through our code. We build the identity and access platform that hundreds of thousands of Swedish companies rely on every day.

We are now looking for a senior developer who wants to take clear technical ownership within our Customer Identity & Access domain (CIAM). This is a role for you who wants to make a real impact: architecture, data modeling, technical choices, and how identity and access are managed on a large scale at one of Sweden's leading product companies.

As a central part of the team building the backbone of identity and access in all Fortnox products, our mission is to provide robust core services and APIs that the entire organization can rely on as the definitive source for secure access data.

One of our biggest technical challenges is multi-dimensional access structures. Our users operate in dynamic contexts where they need to seamlessly switch between isolated environments - agencies managing hundreds of client companies, conglomerates with subsidiaries, and users switching contexts mid-workflow. This requires us to effectively manage granular permissions and complex relationships with high flexibility, performance, and precision.

In this role, you will be a technical leader. You will work closely with other senior developers, architects, and product teams to ensure that our CIAM platform is scalable, secure, and easy for other teams to integrate with.

Job Responsibilities

As a senior developer with us, you will work on solving complex problems through code and design. Your days will be filled with:

• Taking technical ownership: Drive architecture and technical choices for how we handle identity and access in distributed systems.
• Designing core services: Build backend services that act as the engine for authorization and identity in a modern microservices architecture.
• Modeling complex data logic: Find solutions for scenarios where permissions are inherited, delegated, and isolated in advanced hierarchies and relationships.
• Owning API contracts and developer experience: Be responsible for creating clear interfaces, "golden paths," and integrations that other developers love to use.
• Strengthening application security: Proactively work to build security (Secure by Design) directly into the architecture.
• Acting as a technical mentor: Serve as a stepping stone for other developers and contribute to a strong engineering culture.

About You

This is a role for someone who is highly experienced, confident in their technical skills, and identifies as a system developer first and foremost. You thrive in the heart of the system where the demands for data consistency, performance, and availability are at their highest. You see identity and access not just as a security requirement, but as an architectural cornerstone.

We believe you will recognize yourself in:

• Many years of experience in backend development (we primarily code in Java, but welcome experience in e.g. Go) and familiarity with building large-scale platforms.
• A strong understanding of architecture, distributed systems, and how to correctly synchronize data in real time.
• Experience with data modeling and a passion for solving complex hierarchies and relationship structures.
• A good understanding of the modern identity ecosystem. You are familiar with standards like OAuth2 and OIDC, and understand the entire flow from authentication (e.g., Swedish eID/BankID) to complex authorization.
• Ability to see the big picture: development experience, operations, stability, and security.
• Comfortable in a leading technical role without formal managerial responsibility.

It is a big plus if you have specific experience with CIAM in SaaS companies or a deep interest in application security in general.

We Offer

• A strategically important role with a great technical mandate where your decisions affect hundreds of thousands of users every day.
• The opportunity to help build a future-proof identity platform.
• A team with high competence and a strong focus on security.
• Flexible work - work from offices in Växjö, Stockholm, Malmö, Linköping or remotely.
• Access to Fortnox "MåBra" program focused on your well-being and balance in life.
• A culture that combines technical interest with a genuine focus on people and community.

Fortnox – at the heart of business life

Fortnox helps companies start, grow, and develop. With smart technical solutions for companies and accounting firms, flexible financing, and an ecosystem of strong partnerships, Fortnox is a hub for entrepreneurship in Sweden. We are driven by the vision of a prosperous society shaped by successful companies.

Fortnox was founded in 2001 with headquarters in Växjö. Learn more at

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