Senior Backend Engineer (Full-Stack Integration) – Sustainable Tech Unicorn

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**About the client

**

A **German Sustainable Tech Unicorn** that is redefining how global corporations handle transparency. Backed by a **€130M Series C** investment, our client has built a proprietary, serverless cloud infrastructure to ensure human rights and ecological responsibility across global supply chains.

Currently in a massive consolidation phase, their Madrid Hub is expanding from 20 to over 100 top-tier engineers in 2026. This is your chance to join a high-growth environment where engineering quality and product ownership are the top priorities.

**Job description

**

As a **Senior Backend Engineer** , you will be the backbone of our client transparency engine. While your expertise lies in robust server-side architecture, you will own your features from the database to the final user interface, ensuring a seamless bridge between complex ESG data and the end-user experience.

**The Mission

Engineering Beyond the API**

Our client, a German Sustainable Tech Unicorn (€130M Series C), operates a high-scale serverless ecosystem. We need an engineer who doesn't just "hand over" an API, but who understands how data should be consumed and presented to solve critical global supply chain challenges.

**Key Responsibilities

**

Core Backend Excellence

Architect, develop, and maintain high-performance microservices and serverless functions (Node.js/TypeScript).

Full-Feature Ownership

Take responsibility for "vertical" slices of the product. This includes designing the schema, building the logic, and implementing the necessary React hooks/components to bring the feature to life.

System Design

Lead the evolution of our serverless "Hub," focusing on data consistency, security, and scalability.

Contract-First Development

Define and maintain the TypeScript interfaces that unify our backend and frontend, ensuring type safety across the entire stack.

Technical Mentorship

Drive backend best practices while helping the team maintain a high standard of frontend integration and performance.

**Your Profile**

**Backend DNA

** 6+ years of experience with a mastery of **Node.js** and **TypeScript**. You are an expert in asynchronous patterns, API design, and distributed systems.

**Pragmatic Full-Stack Ability

** You are a Backend Engineer by trade, but you are proficient enough in **React.js** to build and maintain the interfaces that power your services. You believe that a "done" feature includes its visual implementation.

**Infrastructure & Cloud

** Strong experience with **AWS (Serverless)**, event-driven architectures, and SQL/NoSQL databases.

**Product Mindset

** You care about the "Why" as much as the "How." You build tools that provide real value to 2,000+ global companies.

**Communication

** Fluent English (C1).

**What’s in it for you?**

**The "Unicorn" Experience

** Impact at scale within a high-density engineering hub in Madrid.

**Hybrid Model

** 3 days office / 2 days remote.

**Tech Sovereignty

** You own the stack. From the database query to the React render, you have the autonomy to build it right.

**Top-Tier Package

** Competitive salary + monthly specialized benefits.