Frontend Developer (Intern)

About the company

Heidi Systems is creating the infrastructure software layer for buildings and energy. The company helps property owners and managers modernize metering, energy-usage tracking, reporting, and billing in a market that is still highly manual across much of Europe.

The team is hiring a frontend engineer to take ownership of the product-facing layer that turns complex infrastructure data into something clear, useful, and responsive. The role centers on the company’s SvelteKit application, which is used daily by property managers, operations teams, and customers.

This is a hands-on position with real data from real buildings. You will work on high-volume consumption information, collaborate closely with backend engineers and the founding team, and be responsible for the quality of what you ship.

What you will do

• Develop and continuously refine the company’s SvelteKit web application.
• Use strongly typed TypeScript throughout the frontend stack.
• Implement routing, server-side rendering, and load functions within SvelteKit.
• Create and maintain reusable interface components using Tailwind CSS and DaisyUI.
• Connect the frontend to backend services through oRPC and help define the boundary between both sides.
• Build dependable tests with Vitest and JSDom.
• Use Bun for runtime execution and command-line scripting tasks.
• Improve developer experience, code standards, and reliability across the frontend.
• Troubleshoot issues spanning APIs, data flows, and the user interface.
• Work directly with the founding team on product direction and architectural choices.

What the company is looking for

The ideal candidate is technically strong, detail-oriented, and product-focused. You should enjoy building polished, performant interfaces on top of complex data systems. You do not need to know everything already, but you should learn quickly, reason from fundamentals, and care deeply about the final outcome.

• 1–2+ years of professional experience using SvelteKit and TypeScript.
• Deep understanding of Svelte reactivity, stores, and the component lifecycle.
• Ability to write strict, idiomatic TypeScript, including generics and utility types, with no implicit any.
• Comfort working in Unix-based development environments.
• A strong focus on code quality, reliability, and practical shipping.
• Interest in working with real data and complex product needs.
• Preference for fast-moving environments with high responsibility and ownership.
• A portfolio or GitHub profile that demonstrates your work.

Tech stack and preferred extras

Primary tools include SvelteKit, TypeScript, oRPC, Tailwind CSS, DaisyUI, Vitest, JSDom, Bun, and Git. Additional experience that would help includes Zod, Drizzle ORM, PostgreSQL, Bun workspaces, authentication patterns such as sessions/JWT/OAuth, professional-level German, and open-source contributions.

Why join

• Work directly with the founding team.
• Take ownership of meaningful technical projects from the beginning.
• Learn how infrastructure software is built in a fast-growing startup.
• Gain exposure to DevOps, data architecture, IoT, energy, and real-estate infrastructure.
• Help define the technical base of a company working in a large, outdated market.
• Enjoy a role with high ownership, steep learning, and strong impact.

Location and start

Berlin is preferred, and a hybrid arrangement may be possible. The team would like someone who can begin as soon as possible.

How to apply

Applicants should send a short introduction, a CV or GitHub profile, and ideally one project they are proud of.

Additional information

This role is described as an internship, but the posting also specifies part-time employment. No stipend or salary amount is provided in the listing. The number of openings is not stated.