Senior Full-Stack Developer

Title: Full Stack Developer Location: Hybrid (Warrington, United Kingdom) Company: GTMaritime (Valstone Portfolio) About the Company: GT Maritime provides mission-critical maritime cybersecurity and communications software to 2,000 companies and 16,000 vessels worldwide — roughly a quarter of the world's non-navy fleet. Based in Warrington, UK, GT Maritime operates as a focused, technically rigorous business with a strong culture of quality and long-term ownership. GT Maritime is part of the Valstone portfolio. About Valstone: Valstone is an industrial software conglomerate that acquires and operates mission-critical software businesses across agriculture, logistics, food processing, bulk materials, and manufacturing. With 19 acquisitions completed across Canada, the USA, and the UK, Valstone takes a long-term, buy-and-hold approach — building businesses rather than exiting them. Valstone is part of the Valsef Group, a Montreal-based holding company. Sister entities include Valsoft (130+ acquisitions, $3B+ valuation), Permanent Corp, Valnet, and Valsef Capital. Valstone at a Glance (Part of the Valsef Group) 19 acquisitions completed4 core verticalsCanada, USA and UK operationsBuy and hold — no exit horizon$200M revenue target by 2026 𝐀𝐛𝐨𝐮𝐭 𝐭𝐡𝐞 𝐑𝐨𝐥𝐞 Reporting to the Head of Engineering, this is a senior, hands-on role with real authority attached: you'll own a core area of GT Maritime's platform end to end. When something breaks in production — a distributed fault with no clear cause, on equipment nobody can reach — you're the one who finds the actual root cause, builds the fix, and gets it safely shipped. You'll own three products end to end: Replicate (file replication between ship and shore), Fastnet (packet transport and bandwidth management) and Deploy (software updates to vessel endpoints) — all C#, .NET and AWS. Beyond writing code, you'll hold pull request authority over other developers' work, own the weekly production release builds across the product estate, and carry the security and stability workload that comes out of penetration testing and ISO 27001. We work Shape Up, in six-week cycles — you get a problem and an appetite, not a spec, and you do the uphill investigation yourself before anything is built. 𝐃𝐞𝐥𝐢𝐯𝐞𝐫𝐲 & 𝐎𝐰𝐧𝐞𝐫𝐬𝐡𝐢𝐩 Design and build complex backend features spanning remote agents, shore-side services and the cloud stack that connects them. Diagnose intermittent, distributed failures from logs and telemetry rather than guesswork, and own delivery end to end — test plan, edge cases, and rollback path included. 𝐐𝐮𝐚𝐥𝐢𝐭𝐲 & 𝐑𝐞𝐥𝐞𝐚𝐬𝐞 Act as a Change Authority: review and authorize pull requests from other developers as if you'd written the code yourself, including running it locally. Produce the weekly production release builds and verify rollback before every release. 𝐒𝐞𝐜𝐮𝐫𝐢𝐭𝐲 & 𝐂𝐨𝐦𝐩𝐥𝐢𝐚𝐧𝐜𝐞 Fix the security findings that come out of penetration testing — authorization defects, credential handling, secret management — and build to ISO 27001 requirements, producing the technical evidence the audit needs. 𝐋𝐞𝐚𝐝𝐞𝐫𝐬𝐡𝐢𝐩 𝐖𝐢𝐭𝐡𝐨𝐮𝐭 𝐃𝐢𝐫𝐞𝐜𝐭 𝐑𝐞𝐩𝐨𝐫𝐭𝐬 Mentor developers by pairing on hard problems and through review feedback that teaches. Document the build and deployment process so no part of the release depends on one person. 𝐌𝐮𝐬𝐭 𝐇𝐚𝐯𝐞 Expert-level commercial C# and .NET: advanced patterns, async and concurrency done correctly, performance and memory workASP.NET Core Web APIs, Entity Framework Core, and long-running Windows services or worker processesReal database depth — schema design, migrations, query optimization, index behavior and transaction isolation (MariaDB/MySQL, SQLite)AWS in production, not just in theory: Lambda, SQS, SNS, DynamoDB, S3, Secrets Manager, CloudWatch — able to debug a live issue from the logsDistributed systems instincts: retries, idempotency, eventual consistency, reconciling two systems that can't always reach each otherApplication security you can act on: authorization and access control, encryption and key management, credential storageAdvanced Git and CI/CD pipelines; code review that catches architectural problems, not just styleAround 8+ years of commercial software development, several at senior level owning features end to end 𝐒𝐡𝐨𝐮𝐥𝐝 𝐇𝐚𝐯𝐞 Windows client/agent software: installers, services, code signing, upgrade and rollbackReal-time messaging (SignalR or equivalent), including tenant isolationMicrosoft Graph, SharePoint or OneDrive integration experienceWorking TypeScript and modern front-end knowledge, enough to finish a feature through the dashboardComfort reading legacy code (C++, Visual Basic)AI-assisted development experience (Claude Code, Amazon Q or similar) as everyday practiceMaritime, satellite comms, or other bandwidth-constrained domain background 𝐖𝐡𝐨 𝐅𝐢𝐭𝐬 𝐓𝐡𝐢𝐬 𝐑𝐨𝐥𝐞 We'd rather fix the cause than escalate the symptom. This is the engineer who independently takes a customer-affecting problem, finds the actual root cause in a distributed system with intermittent faults, and gets the fix safely into production on equipment that's difficult to reach. Maritime experience isn't required — we'll teach you the domain.