Logo for Principal33

API Developer – .NET

Role overview

Qualifications

  • Strong hands-on experience as a .NET API developer or senior engineer
  • Expertise in C#, .NET (Core/5/6/7+) and the modern .NET ecosystem
  • Deep experience designing, building, and consuming APIs (REST and/or gRPC)
  • Proficiency with API tooling and practices: OpenAPI/Swagger, contract testing, API gateways, security best practices

Responsibilities

  • Own the technical direction and architecture for the API surface in your domain
  • Design and evolve API architectures; define contracts, versioning, security, and observability
  • Translate product features into technical designs and actionable work
  • Develop, test, and document APIs; implement contract tests and robust integration tests

About the company

Principal33 logo

Principal33

IT development, Business Transformation, Product thinking, and Design delivered Lean. We offer development resources & End-2-End IT Services & Management to empower your company starting from a single month to a full IT development lifecycle. We are working for companies in the Energy sector, Auto, Pharma, Design, IT development, and Start-ups. Do you have an idea? Do you want to develop a new MVP or test quickly some hypotheses? We can build your product or service from scratches or providing you with the tools you need. If you are interested send us an e-mail to: hello@principal33.com

Company details

Company size201 - 500

Your match analysis

See how your profile stacks up against this role.

We compared the job requirements to your profile to show where you're strong and where you fall short.

Job description

Your mission

Role purpose

A hands-on API developer specializing in .NET API design and delivery within the organization. You will own the implementation of robust, secure, and scalable APIs, advocate API-first practices, and collaborate with Product, Architecture, Security, and Platform teams. 

Primary Focus

  • API design, development, and lifecycle for .NET-based products
  • API-first approach: REST, gRPC, OpenAPI/Swagger, contract testing, versioning
  • Cloud-native integrations, DevOps, CI/CD, and observability
  • Collaboration with Digital Product Owner (DPO), Enterprise Architecture, Security, and Platform teams
  • Balance speedy delivery with long-term maintainability and regulatory awareness as a plus


Your profile

Key Responsibilities

  • Own the technical direction and architecture for the API surface in your domain
  • Design and evolve API architectures; define contracts, versioning, security, and observability
  • Translate product features into technical designs and actionable work
  • Develop, test, and document APIs; implement contract tests and robust integration tests
  • Lead code reviews and ensure consistent coding standards and quality
  • Establish and maintain DevOps practices, CI/CD pipelines, automated tests, and monitoring
  • Collaborate with Platform, Security, and Enterprise Architecture teams
  • Identify, communicate, and mitigate technical risks, dependencies, and debt
  • Support incident resolution and root cause analysis
  • Ensure alignment with non-functional requirements (performance, reliability, maintainability, security)
  • Align with regulatory/compliance requirements where relevant (treated as a plus)


Required Qualifications

  • Strong hands-on experience as a .NET API developer or senior engineer
  • Expertise in C#, .NET (Core/5/6/7+) and the modern .NET ecosystem
  • Deep experience designing, building, and consuming APIs (REST and/or gRPC)
  • Proficiency with API tooling and practices: OpenAPI/Swagger, contract testing, API gateways, security best practices
  • Solid understanding of cloud-native architectures and integrations; experience with Azure or AWS
  • Proficient in DevOps, CI/CD, automated testing (unit, integration, contract), and observability/monitoring
  • Strong collaboration and communication skills; effective with DPO/EA/security teams
  • Awareness of security, privacy, and audit considerations in API data


Nice-to-Have

  • Experience with interoperability standards or cross-domain integration 
  • Regulatory/compliance domain experience is a plus but not required
  • Containerization and orchestration (Docker, Kubernetes)
  • Advanced observability tools and APM solutions


Skills and Competencies

  • Technical execution: delivers robust APIs with high code quality and maintainability
  • API craftsmanship: strong focus on contracts, versioning, security, and observability
  • Decision making: clear technical choices with well-communicated trade-offs
  • Collaboration: works effectively with Product, Architecture, Security, and Platform teams
  • Quality focus: integrates security, privacy, and regulatory considerations into design and delivery


Collaboration and Stakeholders

  • Digital Product Owner (primary counterpart)
  • Domain engineers and developers within the API team
  • Enterprise Architect
  • Platform teams (Cloud, Integrations, Analytics)
  • Security, infrastructure, and operations teams
  • External vendors and implementation partners


Decision Authority

  • Technical design and implementation choices within the API domain
  • Day-to-day technical prioritization and team execution
  • Technical risk mitigation, debt management, and release readiness
  • Engineering practices, tooling, and development workflows within agreed standards


Location and Working Model

  • Valencia, Spain
  • Hybrid / remote-friendly depending on policy and team needs


Background & Experience

  • Strong background as a senior engineer or API specialist
  • Experience delivering API-centric products in agile teams
  • Proficient with cloud platforms, modern architectures, and DevOps practices
  • Ability to collaborate with Enterprise Architecture on standards
  • Experience in enterprise-scale or regulated environments is a plus



What we offer

  • Medical insurance: Your health, and your family's, is our top priority. You're fully covered.
  • Holiday flat in Valencia: Dreaming of sunny days in Spain? Our company flat is ready for your next getaway.
  • Gifts for special occasions: We love celebrating you. Expect thoughtful surprises on Easter, Women's Day, Father's Day, and more.
  • Anniversary gifts: Your 1st, 5th, and 10th work anniversaries are milestones worth celebrating, and we mark each of them with a special gift.
  • Team-building events: We value connection beyond work, offering engaging team experiences in great locations to inspire collaboration and fun.
  • End of year celebrations: We wrap up each year with a special celebration, filled with joy, laughter, and unforgettable moments.
  • Day off on your birthday: Your special day is yours to enjoy, no work required.
  • Community and social initiatives: We bring people together through activities like Bring Your Kids to the Office Day, donation drives, tree planting, sporting events, decorating the Christmas tree with your colleagues, celebrating new office openings, Principal33's anniversary, and more.
  • Access to Udemy: Growth matters, so you get unlimited access to thousands of courses. Develop your skills anytime, anywhere.
  • German language courses: Dedicated courses to help you build your German skills, supporting both personal and professional growth.
  • Personal and professional growth: We support your development through masterclasses with experienced trainers, and we're open to investing in courses and training that help you grow.


Email address

Apply once. Then go straight to the hiring manager.

After you apply, unlock the direct contact details of the people who actually make the call. A quick follow-up makes you 5x more likely to land an interview.

MR

Marcus Rivera

Chief Revenue Officer

m.rivera@company.com
linkedin.com/in/marcusrivera
Unlocked after you apply
·

API Developer Related jobs

Other jobs at Principal33

Premium

Reach out to the hiring manager directly.

Gain access to the contact details of the hiring managers who actually decide, and reach out to network with them directly. That, plus more when you upgrade:

  • Full match report with fit score and gaps
  • Career diagnostics on how recruiters read you
  • Curated company matches and warm intros
  • 48h early access to new roles

Cancel anytime.