{"id":3554493,"url":"https://alion.io/job/firstup-sr-software-engineer-fullstack-uk-2","title":"Sr. Software Engineer, Fullstack (UK)","company":{"id":46276,"name":"Firstup","domain":"firstup.io","url":"https://alion.io/company/firstup-io","size_band":"501-1000","is_staffing_agency":false,"employer_type":"direct","is_intermediary":false,"listed_via":null,"ats_vendor":"Lever","truth_index":null},"role":"Backend","role_family":"Backend","seniority":"senior","employment_type":"full_time","work_mode":"hybrid","remote_scope":null,"remote_scope_basis":null,"remote_working_hours":null,"hiring_geo_confidence":"explicit","locations":["London, United Kingdom"],"countries":["GB"],"hiring_countries":[],"hiring_countries_total":0,"salary":null,"salary_estimate":{"min_usd":90000,"max_usd":175000,"period":"year","method":"role_seniority_country_remote_cell","sample_n":139},"experience_years_min":null,"visa_sponsorship":false,"relocation_package":false,"has_equity":false,"technologies":[{"name":"Claude","optional":false},{"name":"Copilot","optional":false},{"name":"Go","optional":false},{"name":"Node JS","optional":false},{"name":"React.js","optional":false},{"name":"Ruby","optional":false},{"name":"Ruby on Rails","optional":false},{"name":"Shift-Left Security","optional":false},{"name":"TypeScript","optional":false},{"name":"JavaScript","optional":true}],"status":"live","first_seen_at":"2026-10-30T20:09:19Z","employer_posted_date":"2026-10-30","last_verified_at":"2026-11-04T04:43:01Z","board_verified":true,"closed_at":null,"days_open":4,"trust":{"level":"ok","repost_count":null,"flags":[],"days_open":4},"description":"Job Summary\nWe're looking for a Senior Full Stack Engineer who thrives at the intersection of craft and scale. You'll design and deliver large-scale, multi-tenant cloud services - with a relentless focus on availability, fault-tolerance, and elegant architecture. You'll set the bar for engineering quality and help elevate those around you.\nResponsibilities\nCore Engineering & Ownership: Build and own scalable SaaS applications end-to-end - frontend, backend, and data layers. Write production-grade code that is reliable, readable, efficient, and testable. Raise the bar through thoughtful code reviews and comprehensive documentation.\n\nSystem Architecture: Design future-ready architectures and proactively close gaps before they become problems.\n\nPerformance & Reliability: Drive system availability and performance - investigate, analyze, and resolve reliability issues across the stack. Recognize opportunities and advocate for better performance and efficiency of software, systems, and processes across teams.\n\nShift Left Testing & Quality: You champion a rigorous 'shift-left' quality culture, embedding comprehensive testing-unit, integration, and contract-early and continuously in the development lifecycle, not as an afterthought.\n\nAI Integration: Leverage and advocate for AI-assisted tools (e.g., GitHub Copilot, Claude) to accelerate development while maintaining rigorous engineering judgment and accountability for code correctness.\n\nLeadership: Drive team-wide best practices, conduct quality code reviews, and mentor engineers to elevate overall engineering quality.\n\nCollaboration (Product & Design): Partner with Product and Design to translate requirements into intuitive UI, making informed technical trade-offs in the face of ambiguity.\n\nCollaboration (Engineering Standards): Champion engineering best practices across teams and collaborate on solving complex, high-impact problems.\n\nMinimum Qualifications\nBachelor's degree in Computer Science or related field, or equivalent experience.\n\n8+ years building reliable, performant applications and microservices in production environments. Proven full stack fluency - you're comfortable across frontend, backend, and the database layer.\n\nA polyglot mindset - you evolve with the tech. Familiarity with Ruby on Rails, TypeScript, Node.js, Go, or React.js is a strong plus.\n\nProven full-stack experience across frontend (React.js), backend, and database layers.\n\nContribute to production health, including on-call rotations and incident response, in a \"you build it, you run it\" environment.\n\nTechnical depth in at least one engineering domain: distributed systems, multi-tenant SaaS, application databases, networking, security, serverless, event streaming, or similar.\n\nA genuine drive to build beautiful, intuitive products with the customer always in focus. Innate curiosity - you love learning and have a desire to teach and lift others. Strong communication skills and openness to collaborative idea-sharing across teams.\n\nPreferred Qualifications:\nCore Stack Experience: Familiarity with Ruby (including Ruby on Rails), TypeScript, Node.js, Go, or React.js is a strong plus.","description_format":"text","description_chars":3154,"description_truncated":false,"requirements":{"experience_years_min":null,"management_years_min":null,"team_size_min":null,"manages_managers":false,"education":{"level":"bachelor","optional":false},"security_clearance":false,"languages":[]},"benefits":[],"hiring_locations":[{"name":"United Kingdom","iso":"GB","kind":"country"}],"hiring_excludes":[],"relocation_offered":false,"industries":["Team Communication & Collaboration","Intranet & Knowledge Management"],"lifecycle":[{"event":"open","at":"2026-10-31T00:11:37Z"}],"visa":[{"country":"GB","licensed_sponsor":true,"evidence":"Licensed UK visa sponsor (Skilled Worker, Senior or Specialist Worker)","filings_12m":null,"filings_prev_12m":null,"green_card_filings_12m":null,"median_offered_wage_usd":null,"route":"Skilled Worker; Global Business Mobility: Senior or Specialist Worker","cap_exempt":false,"checked_at":"2026-11-03T08:26:00+00:00","sources":["UK Home Office: register of licensed sponsors (workers)"],"filings_for_role_12m":0}],"liveness":{"score":86,"band":"hot","label":"Hiring now","p_open":1,"p_active":0.86,"p_room":1,"age_days":3,"expected_fill_days":47,"reasons":["conf:2","win:early"],"computed_at":"2026-11-03T05:54:40Z"},"pay":null,"html_url":"https://alion.io/job/firstup-sr-software-engineer-fullstack-uk-2","json_url":"https://alion.io/job/firstup-sr-software-engineer-fullstack-uk-2.json","meta":{"generated_at":"2026-11-04T05:31:34Z","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":8610,"day_limit":null,"remaining_today":null,"minute_limit":300,"resets_at":"2026-11-05T00:00:00Z"}},"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":46276},"rest":"https://alion.io/mcp/rest/get_company?id=46276"},"human":"https://alion.io/catalog?offer=company.slices&for=job%2Ffirstup-sr-software-engineer-fullstack-uk-2"},{"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%2Ffirstup-sr-software-engineer-fullstack-uk-2"},{"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%2Ffirstup-sr-software-engineer-fullstack-uk-2"},{"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/firstup-sr-software-engineer-fullstack-uk-2\", \"note\": \"what you need it for\"}"},"human":"https://alion.io/catalog?offer=company.verify&for=job%2Ffirstup-sr-software-engineer-fullstack-uk-2"}],"agent":{"mcp":"https://alion.io/mcp/jobs","mcp_open":"https://alion.io/mcp/open","next":[{"tool":"get_job","arguments":{"id":3554493}},{"tool":"search_jobs","arguments":{"company":"firstup.io","detail":"compact"}},{"tool":"match_people","arguments":{"job_id":3554493},"note":"people open to offers who fit this vacancy"}],"note":"The same data through MCP tools: https://alion.io/mcp/open needs no sign-in (compact searches, postings, people); https://alion.io/mcp with an Alion account has everything. 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