Principal Software Engineer

All3 is transforming how buildings are conceived, developed, and delivered. We combine AI-powered design with robotic prefabrication and on-site assembly to build custom architecture at the cost and speed of mass production - unlocking even the most complex sites

We’re currently seeking a Principal Software Engineer to join our team, focused on building and evolving the core platform that powers our products. This is not a typical feature-team role. The work would be centered around a shared platform that other products and teams rely on. It includes the common data layer, core services, platform logic, and product-facing tools that sit on top of it.

We need someone senior enough to think at a platform level, but still fully hands-on. You should be comfortable making architectural decisions, aligning with other tech leads, and be ready to implement important parts yourself.

Responsibilities:

• Building core platform services and product functionality end to end;
• Defining and evolving shared backend architecture, APIs, and data models;
• Designing system logic for artifact status, derivations, dependencies, and traceability;
• Ensuring technical consistency across applications built on the platform;
• Translating complex, cross-domain requirements into clear and scalable systems;
• Writing production-ready code across backend and frontend layers;
• Setting technical direction through design work, code reviews, and hands-on implementation.

Requirements:

• Strong experience building complex software systems;
• Experience designing shared platforms used by multiple teams;
• Solid backend development skills in JVM languages such as Kotlin, Scala, or Java;
• Good fullstack judgment and ability to work across system layers;
• Strong system design and architectural thinking;
• Ability to structure complex domains into clear models and workflows;
• Effective communication with senior engineers and technical stakeholders;
• Hands-on mindset with a focus on writing and owning production code.

Would be nice if you have:

• Experience with workflow-heavy or model-heavy systems;
• Experience with traceability, dependency management, or stateful business logic;
• Experience in construction tech, BIM, design tools, engineering software, manufacturing, or other multi-domain products.

We offer:

• Chance to be a part of a large-scale project;
• Team driven by impactful cause;
• Hybrid format of work with spacious office in New Belgrade;
• Private health insurance including dental;
• Language courses;
• Flexible working schedule;
• 20 days of annual leave;
• 5 wellness days per year.