{"id":2205722,"url":"https://alion.io/job/yellowtail-senior-c-developer","title":"Senior C# Developer","company":{"id":174414,"name":"Yellowtail","domain":"yellowtail.nl","url":"https://alion.io/company/yellowtail","size_band":"51-200","is_staffing_agency":false,"employer_type":"direct","is_intermediary":false,"listed_via":null,"ats_vendor":"Recruitee","truth_index":{"grade":"D","score":45,"open_postings":24,"ghost_share":0.917,"stale_share":0,"repost_share":0,"time_to_fill_p50_days":null,"computed_at":"2026-10-12T06:55:09Z"}},"role":"Backend","role_family":"Backend","seniority":"senior","employment_type":null,"work_mode":"on_site","remote_scope":null,"remote_scope_basis":null,"remote_working_hours":null,"hiring_geo_confidence":"explicit","locations":["Naarden, Netherlands"],"countries":["NL"],"hiring_countries":[],"hiring_countries_total":0,"salary":{"min":3400,"max":5300,"currency":"EUR","period":"month","gross":null,"usd_annual":71280},"salary_estimate":null,"experience_years_min":5,"visa_sponsorship":false,"relocation_package":false,"has_equity":false,"technologies":[{"name":"Agile","optional":false},{"name":"Azure","optional":false},{"name":"C#","optional":false},{"name":"Entity Framework Core","optional":false},{"name":"MS SQL","optional":false},{"name":"Angular","optional":true},{"name":"ASP.NET Core","optional":true},{"name":"Azure DevOps","optional":true},{"name":"Blazor","optional":true},{"name":"CI/CD","optional":true},{"name":"JavaScript","optional":true},{"name":"JQuery","optional":true},{"name":"TypeScript","optional":true}],"status":"live","first_seen_at":"2025-11-06T11:04:21Z","employer_posted_date":"2025-11-06","last_verified_at":"2026-10-13T00:07:28Z","board_verified":true,"closed_at":null,"days_open":340,"trust":{"level":"ghost","repost_count":0,"flags":["stale","company_stale"],"days_open":339},"description":"Digital Resilience\nAt Yellowtail Conclusion, we develop software that strengthens digital security in one of the most digitized countries in the world: the Netherlands. One of our flagship products, Key Control Dashboard (KCD), enables organizations to manage risks effectively through smart, user-friendly technology.\nTo keep innovating, we’re looking for a Senior Developer. In this role, you are responsible for the technical realization of developing and maintaining our software, together with the team based in The Netherlands.\nWhy is Senior C# Developer your next job?\nAs a Senior Developer, you are responsible for influencing, designing, and building roadmap items. You are hands-on in resolving technically complex issues for our customers, collaborating with our development team. You consistently consider the 'bigger picture' for both our customers and for KCD. There are ample opportunities within KCD to truly leverage your specific skills and qualities.\nYou can play a vital role in both modernizing the application and add new innovative functionality;\n\nWe encourage learning and experimentation. Have an idea to improve performance or user interaction? We want to hear it, and help you test it;\n\nGrowth and ownership. You’ll be trusted with real responsibility, contribute to technical decisions, and mentor junior developers as part of a collaborative team;\n\nWe truly value your talent and want to support your growth. At KCD, you will have ample learning opportunities and the freedom to discover your strengths.\n\nRequirements\nWhat we think is important:\nAs a Senior Developer, you have numerous opportunities, freedom, and the ability to shape the future. We have confidence in your ability to do what is necessary. For that, you need to possess:\nA relevant bachelor’s or master’s degree in Computer Science, Software Engineering, or a related field.\n\n5+ years of professional development experience.\n\nStrong experience with C# (.net framework and.net core)\n\nDemonstrable knowledge and experience with data & software security;\n\nKnowledge of C#, .NET full stack, entity framework, MS SQL Server and Azure;\n\nKnowledge of API management;\n\nAI adopter\n\nA proactive mindset with strong communication skills in English (Dutch is an advantage).\n\nTeam spirit: you enjoy collaboration, providing constructive feedback, and contributing to a dynamic team.\n\nExperience working within agile development teams and a solid track record of independently solving technical challenges.\n\nOur Tech Stack\n Front end: .net MVC, jQuery, optionally Blazor or Angular\nBack end: C#, ASP.NET\n\nData & cloud: MS SQL Server, Azure\n\nDevOps: CI/CD pipelines, code reviews, automated testing\n\nYou’ll primarily work on the .net core back end but have the opportunity to contribute across the stack if desired.\n\nWhat’s in it for you?\nSalary between €3900 and €5300 gross per month;\n\n€767,25 mobility budget per month (can be used for travel expenses or as additional salary);\n\nAll essential matters well-organized: a high-speed laptop, phone, excellent pension plan, travel allowance, and daily lunches;\n\nFlexible working: largely choose where and when you work. We believe in maintaining a healthy work-life balance and support you in setting up a comfortable home office or even working remotely from your favorite vacation spot;\n\nA friendly, informal culture: we frequently organize activities such as company trips, hackathons, sports events, and more. Every other year, there’s either a major company trip or a large-scale hackathon;\n\nRoom for personal growth: you will receive mentoring and coaching from senior developers, enabling you to quickly learn and advance.","description_format":"text","description_chars":3659,"description_truncated":false,"requirements":{"experience_years_min":5,"management_years_min":null,"team_size_min":null,"manages_managers":false,"education":null,"security_clearance":false,"languages":[{"language":"English","level":"All levels","optional":false}]},"benefits":["Flexible schedule","Home office","Professional development"],"hiring_locations":[{"name":"Netherlands","iso":"NL","kind":"country"}],"hiring_excludes":[],"relocation_offered":false,"industries":["Design & Creative","Web Design","Digital Design"],"lifecycle":[{"event":"open","at":"2026-10-09T23:19:40Z"}],"visa":[],"liveness":{"score":5,"band":"cold","label":"Long shot","p_open":1,"p_active":0.195,"p_room":0.28,"age_days":339,"expected_fill_days":37,"reasons":["conf:3","stale_co","ghost","win:tail","crowd:"],"computed_at":"2026-10-12T06:55:09Z"},"pay":{"stated_usd_annual":71280,"is_top_pay":false},"html_url":"https://alion.io/job/yellowtail-senior-c-developer","json_url":"https://alion.io/job/yellowtail-senior-c-developer.json","meta":{"generated_at":"2026-10-13T03:22:18Z","cache_seconds":300,"methodology":"https://alion.io/methodology","terms":"https://alion.io/terms","contact":"https://alion.io/contact","api":"https://alion.io/developers","about":"Alion is a live layer of people, companies and AI agents: who they are, whether they are real and active right now, what they do and how to work with them, readable by people and by agents and paid per call.","catalog":"https://alion.io/catalog.json","usage":{"tier":"crawler_verified","counted_by":"address","units_charged":1,"used_today":5242,"day_limit":null,"remaining_today":null,"minute_limit":300,"resets_at":"2026-10-14T00:00:00Z"}},"offers":[{"id":"company.slices","title":"One company in depth, by slice","status":"live","price":{"credits":0.02,"usd":0.002,"plus_per_slice":{"credits":0.05,"usd":0.005}},"unit":"per company, plus each slice with data","note":"the employer in depth","call":{"mcp_tool":"get_company","arguments":{"id":174414},"rest":"https://alion.io/mcp/rest/get_company?id=174414"},"human":"https://alion.io/catalog?offer=company.slices&for=job%2Fyellowtail-senior-c-developer"},{"id":"market.stats","title":"A market slice: pay, demand and time to fill","status":"live","price":{"credits":1,"usd":0.1},"unit":"per slice","note":"pay, demand and time to fill for this role and place","call":{"mcp_tool":"market_stats"},"human":"https://alion.io/catalog?offer=market.stats&for=job%2Fyellowtail-senior-c-developer"},{"id":"job.search","title":"Open jobs by role, technology, place, pay and visa","status":"live","price":{"credits":0.02,"usd":0.002},"unit":"per posting in a list","note":"similar open postings","call":{"mcp_tool":"search_jobs"},"human":"https://alion.io/catalog?offer=job.search&for=job%2Fyellowtail-senior-c-developer"},{"id":"company.verify","title":"Is this company real and active right now","status":"pilot","price":null,"unit":"per company","request":{"url":"https://alion.io/catalog/request","method":"POST","body":"{\"offer\": \"company.verify\", \"for\": \"job/yellowtail-senior-c-developer\", \"note\": \"what you need it for\"}"},"human":"https://alion.io/catalog?offer=company.verify&for=job%2Fyellowtail-senior-c-developer"}]}