.NET Backend Engineer

We’re Kabilio , a company backed by two leading venture capital firms, founded by experienced entrepreneurs, Alex Valls and Jose Ojeda , with a strong track record in building and scaling successful tech companies.

What We’re Building

Our goal is to become the go-to Financial Operating System for accounting firms and SMEs in Southern Europe , unifying accounting, tax, payments, planning, and banking into a single platform. We are currently a tight-knit team of 50+ people and plan to grow in 2026, with a strong focus on engineering, product design, and sales.

Why this role matters?

Today, Kabilio already runs three core products in production — Invoices Processing, Bank Transactions, and Invoicing — used daily by real customers. At the same time, we’re building our Accounting platform, the product that defines our long-term vision and the reason Kabilio was founded. AI sits at the core of everything we build, from automating and categorizing financial data to enabling intelligent workflows and decision-making across the entire financial lifecycle. We rely on modern architectures and proven technologies to turn this vision into a scalable, production-ready platform.

As a Senior .NET Engineer at Kabilio, you will take ownership of a core backend system that is critical to the company and our customers. This system operates independently from our main platform and supports key business workflows under strict client and regulatory constraints.

Due to customer and compatibility requirements, this system is built on .NET Framework 4.8 and relies on mature, well-established libraries. This role requires strong engineering judgment, deep experience, and a pragmatic approach to maintaining and evolving software in real-world constraints. While the platform is constrained by customer requirements, there is room to improve internal structure, reliability, and tooling over time.

What you’ll do?

• Take technical ownership of a core, isolated .NET system used in production.

• Maintain, extend, and stabilize an existing codebase built on .NET Framework 4.8.

• Ensure reliability, performance, and correctness in a business-critical environment.

• Diagnose and resolve complex production issues.

• Collaborate with other engineering teams to ensure correct integration points.

• Make pragmatic decisions balancing risk, maintainability, and business needs.

• Gradually improve code quality and internal structure where possible.

What we offer?

• Salary range: Competitive salary (TBD in the first call).

• Flexible benefits via Cobee.

• Hybrid setup : 3 days/week in our Barcelona office. The home office days give you time to focus and the flexibility to plan your day around your productivity peaks.

• Indefinite Spanish Contract + top work equipment

• Opportunity : Enter a massive market ready for disruption. We have a clear strategy to make our mark in Spain, leveraging what we have seen in other markets.

• Collaborative and Growth Culture : We prioritize open communication and respectful discussions. Your ideas will have a real impact, and you will have the chance to shape and grow with the business

What should you bring to the table?

• Senior-level experience building and maintaining production systems with .NET.

• Hands-on experience with .NET Framework (not only .NET Core / .NET 6+).

• Strong understanding of Windows Service lifecycles, installation, startup behavior, and recovery options

• Proficiency in using and integrating dynamic link libraries (DLLs) to interface with other Windows software

• Experience with Windows Installer (MSI/WiX/Inno Setup)

• Familiarity with inter-process communication (IPC) techniques

• Understanding of system-level Windows APIs

• Strong understanding of relational databases and transactional systems.

• Proven ability to work with legacy or constrained systems responsibly.

• Calm, methodical approach to debugging and problem solving. Comfortable working autonomously with high ownership.

• Professional level Spanish, and English (B1 should be enough).

• Above all, you’re a reliable and trustworthy person

Nice to have

• Experience owning systems that are business-critical.

• Experience in financial, accounting, or regulated domains.

• Experience modernizing or stabilizing legacy systems.

• Exposure to system integration or migration projects.

Hiring process

1. Video call with Sofia → Get to know you each other (30 mins) → Book the first call here

2. Video call with Ivan Rodriguez (30 minutes)

3. Technical test with the team (60 minutes)

4. Meeting with founders on-site → Job offer