Backend developer

Mission Overview:

Keystone Solutions is hiring a Senior Back-end Developer to join our consultancy team and deliver a mission for our client in Brussels. As a Keystone Solutions consultant, you will work closely with the client's product and platform teams, contributing hands‑on to back‑end services built on modern .NET and Azure, while benefiting from Keystone's community, coaching, and project diversity. This engagement requires on‑site presence at the client location at least 2 days per week.

About Keystone Solutions' Consultancy Model:

As a Keystone Solutions consultant, you are employed by Keystone and embedded within our client's squads to design, build, and operate solutions on‑site and remotely. You collaborate with client stakeholders while being supported by Keystone mentors, practice leads, and a strong internal knowledge network. Over time, you may rotate across projects and industries, gaining breadth without sacrificing depth.

Key Responsibilities:

• Translate application storyboards and use cases into functional application
• Design, build, and maintain efficient, reusable, and reliable code
• Integrate data storage solutions, which may include relational databases, key‑value stores, blob/object stores, and similar technologies
• Ensure the best possible performance, quality, and responsiveness of applications
• Identify bottlenecks and bugs, and devise solutions to mitigate and address these issues
• Help maintain code quality, organization, and automatization
• Work with central teams to enhance the DEVOPS capability of the development teams

All the responsibilities above will be performed on the client project as a Keystone Solutions consultant.

Conformity Criteria:

• Minimum 10 years of professional experience in .NET development, demonstrated in the CV, including recent experience with .NET Core/.NET 8-10 or equivalent versions and REST API development
• Minimum 5 years of hands‑on experience with Microsoft Azure in a professional context
• Minimum 5 years of experience in DevOps practices, including CI/CD pipelines (e.g. YAML), and deployment strategies such as blue/green deployment
• You communicate fluently in English (spoken and written), at least level B2
• Willing to work on‑site at least 2 days per week (Brussels)

Evaluation Criteria:

For each evaluation criterion, the expectation is that your CV clearly demonstrates relevant experience or knowledge through one or more examples/projects. The more relevant experience or knowledge you can provide as evidence, the better your CV will be evaluated.

• Depth and relevance of experience with Microsoft Azure
  • Scope of services used (e.g. Event Hub, Cosmos DB, Functions, etc.)
  • Level of responsibility and role
  • Complexity of projects
• Level of expertise in .NET development
  • Experience with modern .NET practices (e.g. microservices architecture, feature flags, clean architecture)
  • Role and responsibilities in previous projects
• Experience with software architecture
  • Application of design patterns and microservices architecture in previous projects
  • Scope and impact of implemented solutions
• Experience with databases
  • Practical experience with SQL and NoSQL databases
  • Context of usage (transactional systems, distributed systems, etc.)
• Experience with testing practices
  • Implementation of unit testing (tools, frameworks, coverage context)
• Experience with version control tools
  • Practical use of Git in collaborative environments
• Experience with development and collaboration tools
  • Use of Atlassian suite (Jira, Confluence, etc.)
  • Context of usage (Agile delivery, DevOps processes)
• Experience with Agile methodologies
  • Type of methodologies used (Scrum, SAFe, etc.)
  • Role and level of involvement
• Continuous learning and innovation (reformulation of soft skill)
  • Evidence of adoption of new technologies or frameworks in previous projects
  • Participation in innovation initiatives or modernisation efforts
• Front‑end experience
  • Experience with React.js in professional projects
• AI IDE experience (bonus)
  • Relevance experience in development with AI

What You Will Gain as a Keystone Solutions Consultant:

• Consultancy nature of work: You will be a Keystone Solutions consultant embedded with the client's teams, combining on-site collaboration in Brussels (minimum two days per week) with remote work, delivering tangible outcomes while representing Keystone's standards.
• Dynam