Founding Engineer

90/10; Berlin; Vor Ort; EUR 60.000 - 100.000; Vollzeit

Benefits dieser Stelle

Founding-level influence

Equity opportunity

Competitive salary

Zusammenfassung

90/10 is building a single platform where data and decisions behind an offer come together for construction companies. Our ambition is to become the go-to platform for calculation across the construction industry, starting with technical building equipment (TBE).

We are hiring our first engineer to build the product and the company with us in Berlin. You will own the product end-to-end, work with TypeScript/React, Convex, and Mastra, and shape architecture, security, and development workflow.

Qualifikationen

• 3+ years of software engineering experience.
• Strong focus on types, interfaces and data models.
• Ability to own a product end-to-end from problem to deployment.
• Experience with frontend TS/React and production systems.

Aufgaben

• Own core product end-to-end from idea to deployment.
• Connect unstructured documents with diverse data sources.
• Balance model-driven, rule-based, and human-confirmed AI approaches.
• Improve performance and usability for real tenders at scale.

Kenntnisse

Product mindset

Self-directed

Team collaboration

Data modeling

Tools

TypeScript

Tanstack/React

Convex

Mastra

Jobbeschreibung

We are building 90/10 because construction companies need one place where all the data and decisions behind an offer come together. Our ambition is to become the single platform for calculation across the construction industry: starting with technical building equipment (TBE).

Our current pipeline contains meaningful test and pilot opportunities, with companies already in onboarding or an active test phase. Now we are looking for our first engineer to build the product and company with us.

What You’ll Work On

• Core product: Connect unstructured documents with different data sources, reliable and traceable.
• AI systems: Decide what should be model-driven, rule-based, or confirmed by a human.
• Full-stack product: Improve performance and usability for real tenders with hundreds or thousands of positions.
• Engineering foundations: Shape our architecture, security standards, development workflow, and future engineering team.

Who We’re Looking For

• You have built, operated and own a product end to end, ideally in an early-stage B2B environment.
• You use AI heavily without outsourcing your judgement to it.
• You can turn an unclear customer problem into a simple product decision and take responsibility for what happens after deployment
• You do not need a construction background but the curiosity to understand why a unit, price basis, material surcharge, or labor-time assumption can move an offer by five figures

Technical

• 3+ years of experience in software engineering
• Care about types, clear interfaces and sensible data models
• Comfortable owning production systems, debugging failures, and protecting sensitive customer data
• TypeScript-only: Tanstack / React, Convex and Mastra. Convex experience is useful, but strong fundamentals matter more

Mindset

• Product-minded: You care more about solving the right customer problem than producing more code.
• Self-directed: You move from ambiguity to action and communicate trade-offs proactively.
• Company first, ego second: You challenge decisions, welcome feedback, and optimize for the best outcome.

What You Get

• Founding-level influence: Shape the product, architecture, engineering culture, and team from the beginning.
• Meaningful responsibility: Competitive salary and equity appropriate for our first engineering hire.
• The tools you need: Modern hardware, AI tooling, and a development setup designed for speed.

Interview Process

1. Intro call: Meet a founder and align on the role and stage (~30 min)
2. Technical deep dive: Discuss systems you have built and how you approach real 90/10 problems (~60 min)
3. Working session: Solve a representative product and architecture problem together. No unpaid take-home project (~60 min)
4. Founder conversation: Align on ownership, working style, compensation, and the company we want to build (~60 min)