Senior Full Stack Engineer

NestAi Oy; Helsinki; On-site; EUR 90,000 - 120,000; Full time

Benefits offered by this job

Healthcare (occupational)

Flex benefit

Lunch benefit

Team lunches

Mac/PC choice

Holiday allowance

Phone benefit

Expanding benefits

Job summary

NestAI is seeking a Senior Fullstack Developer in Helsinki to design, build and evolve the operator-facing software at the heart of our platform. You’ll deliver scalable web applications with a focus on reliability, performance and a great user experience.

You’ll work across the full stack—from UI in TypeScript/React to API integrations and system performance—collaborating with engineering teams and field leads to surface real-world feedback into the product.

Qualifications

• 5+ years of professional software engineering on production web apps.
• Strong TypeScript and React experience.
• Experience designing and maintaining APIs.
• Fluency with modern CSS and build tooling.

Responsibilities

• Build operator-facing web applications across the stack.
• Collaborate with Forward Deployed Engineers and field leads.
• Improve performance, reliability and user experience.
• Design scalable API interfaces consumed by other developers.

Skills

5+ years software engineering

TypeScript and React

API design

UI/UX attention

Monorepos

Tools

MapLibre

deck.gl

Cesium

Web Workers

React 19

Job description

Company

NestAI builds the adaptive operating system for modern battlefield operations. Most AI systems are built once, validated at deployment, and expected to stay sufficient after that. That assumption holds until conditions change, and in defence, they always do. Our team develops adaptive intelligence for unmanned and command systems: AI that continuously learns from operational data and adapts to changing conditions, deployed in environments where there is no internet, no GPS, and failure is not an option. NestOS, our open, modular, and interoperable platform, enables this at scale and keeps capability evolution under sovereign European control.

Founded in 2025 by Peter Sarlin, whose previous company Silo AI became Europe's largest AI acquisition, NestAI has grown to over 200 engineers and scientists and partners with leading European defence forces and industry. We're ambitious about what we're building and honest with each other. The bar is high, and so are the standards we hold ourselves to. But this is also a place built on humility, trust, and looking after each other. If that sounds like the kind of work you want to do, keep reading.

Join us as a Senior Full Stack Engineer

We are looking for a Senior Fullstack Developer to join our team. This is a role for a skilled engineer who thrives on solving complex problems, building scalable web applications, and delivering intuitive user experiences. You will help build and evolve the operator-facing software at the heart of our platform—interfaces that users and decision-makers rely on when precision and reliability matter most.

As a Senior Fullstack Developer, you will work across the entire technical stack—from design and architecture to front-end execution, API integrations, and system performance. You will collaborate closely with engineering teams and field leads, ensuring real-world feedback shapes our core software platform.

What you’ll work on

• Operator-facing applications built from independently deployed micro-frontends
• Shared packages that other teams build on.
• High-volume, real-time visualization on web-based maps.
• Close collaboration with Forward Deployed Engineers, who take our software into partner environments and bring field feedback back to the product.

What We're looking for

• 5+ years of professional software engineering, most of it on production web applications in TypeScript and React.
• A solid model of how React renders and why. Hands-on experience with React 19 and its concurrent features (actions, transitions, the compiler) is a plus. If you haven’t used them in production yet, we’ll help you catch up.
• An eye for detail in layout, typography, motion and keyboard interaction behaviour.
• Experience designing and maintaining APIs that other developers depend on. You think about the person calling your code and what happens to them when you change it.
• Fluency with modern CSS, the browser platform, build tooling and monorepos.

Nice to have

• Production experience with micro-frontend architectures, including host and remote contracts, shared runtimes, and independent releases
• Hands-on work with geospatial rendering, mapping libraries like MapLibre, deck.gl, or Cesium, or GPU-accelerated visualizations
• Handling real-time, high-frequency browser data using streaming, binary formats, and Web Workers
• Open-source library maintenance for active user bases or design system development
• Experience in defense, aerospace, or other high-consequence domains where software reliability is critical

If your background doesn't match every requirement but the work resonates with you, we'd encourage you to apply. How you think, learn, and take ownership matters more to us than ticking every box.

Why join NestAI

At NestAI, you’ll build meaningful, real-world technology as part of a world-class team of engineers, scientists, and experienced professionals. You’ll work on systems where reliability genuinely matters, contribute to Europe’s security and resilience, and solve problems that demand depth, trust, and craftsmanship.

If you want to build with purpose - and with leading experts in the field - you’ve come to the right place.

What we offer

We offer a growing set of practical benefits to support your work and wellbeing, day to day:

• Occupational healthcare (currently provided by Mehiläinen)
• Epassi Flex benefit (sports, culture, commuting, wellbeing)
• Lunch benefit (25% tax-free coverage)
• Regular team lunches and all-hands events
• Your choice of Mac or PC
• Holiday allowance (50% of holiday salary)
• Phone benefit according to company policy (subscription and device)
• We are continuously developing and expanding our benefits as we grow.

Practicalities

Employment is subject to applicable security screening (including SUPO, where required).

NestAI is an equal opportunity employer. We consider all applicants based on their skills, experience, and potential.