Senior Full Stack Engineer – Vialto Rewards - in London

Vialto is a market leader in global mobility services. Our purpose is to ‘Connect the world’. We are unique and the only stand‑alone global mobility business. This presents a rare opportunity for our clients, stakeholders and colleagues. Our teams help companies streamline and effectively manage their global mobility programs in a cost‑efficient and compliant manner. Our services focus on providing cross‑border compliance and risk assessment for tax, immigration, business travel, rewards and compensation, and remote work. Working at Vialto is about getting the chance to be part of a global and dynamic team. Globally, Vialto has over 8,000 staff and continues to grow. You will work with clients from a range of industries and different geographical locations. We believe in connecting the world and supporting our colleagues to do the same in their careers by undertaking assignments and opportunities globally that broaden their skills and ultimately benefit our clients. Vialto is unstoppable when we work together in a culture of belonging, where everyone can thrive. We encourage employees to bring their true selves and share their unique talents and expertise to positively impact the communities we serve.

Role Summary

Vialto is hiring a Senior Full Stack Engineer to design, build, and operate secure, scalable products that power our Compensation Collection, Shadow Payroll, and Equity offerings for the world’s most complex multinational employers. You will deliver hands‑on engineering across Next.js and React front ends and C# and .NET services running on Microsoft Azure, working in a highly regulated, multi‑jurisdictional environment where accuracy, auditability, and data privacy are non‑negotiable. This role is for an experienced engineer who can own end‑to‑end features—from cross‑border compensation data ingestion to shadow payroll calculation engines to equity event processing—contribute to architectural decisions and consistently deliver production‑ready solutions using agentic development practices including spec‑driven development and agent‑driven development with tools such as Claude Code and Codex. You will build AI‑native products and workflows, embedding AI capabilities directly into compensation, payroll, and equity workflows to reduce manual effort and improve global mobility outcomes.

What You’ll Do

• Build and evolve modern web experiences for Compensation Collection, Shadow Payroll, and Equity products using Next.js, React, and TypeScript with a focus on performance, reliability, and clarity for tax, payroll, and mobility operators.
• Design and implement backend services and APIs using C#, .NET, and WebAPI to support compensation data ingestion, cross‑border payroll calculations, equity event processing, and integrations with client HR, payroll, and equity administration systems (e.g., Workday, SAP, ADP, Shareworks, E*TRADE, Carta).
• Deliver Azure‑native implementations of shadow payroll calculation engines, compensation aggregation pipelines, and equity tax event workflows using Microsoft PaaS services, secure patterns, and operational best practices.
• Contribute to system architecture and technical design for multi‑country payroll, compensation, and equity domains, including integration patterns using REST, file‑based feeds, and event‑driven approaches.
• Own production readiness for your work including logging, monitoring and alerting, reconciliation tooling, incident response support, and operational documentation—critical for payroll cycles and equity event deadlines that cannot slip.
• Apply secure development practices appropriate for handling sensitive compensation, payroll, and equity data including privacy, auditability, segregation of duties, and country‑specific data protection requirements (GDPR, SOC 2, country‑level payroll regulations).
• Partner with product, mobility tax, payroll, and equity subject‑matter experts to translate complex regulatory and client requirements into technical plans and deliverables.
• Use agentic development practices including agent‑driven development with Claude Code, Codex, or similar AI coding agents to accelerate design, implementation, testing, and operations across the SDLC.
• Work in a spec‑driven development workflow, authoring detailed specifications—including country‑specific shadow payroll rules and equity tax treatment—that guide both human and AI agent implementation.
• Design and implement AI‑powered features within Compensation Collection, Shadow Payroll, and Equity products including intelligent data extraction from compensation statements, anomaly detection on payroll inputs, LLM‑assisted user workflows, and retrieval‑augmented generation (RAG) over tax and payroll guidance.
• Evaluate, integrate, and operationalize AI APIs, models, and toolchains within application architectures, ensuring responsible AI usage, cost management, and observability—especially where AI touches financially material outputs.
• Mentor and support other engineers through code reviews, pairing, and technical guidance on payroll, compensation, and equity domain patterns.

Required Qualifications

• 5+ years professional software development experience building enterprise web applications and services, ideally including payroll, compensation, equity, HR, finance, or tax domains.
• Strong experience designing and building large JavaScript applications with Next.js and/or React (TypeScript, state management, performance optimization).
• Strong backend development experience in C# and .NET (ASP.NET, WebAPI, MVC) including API design and service patterns for high‑integrity calculation and data‑processing systems.
• Proven experience with Microsoft Azure designing and building cloud solutions using PaaS services, frameworks, and operational tooling.
• Experience delivering systems in regulated or compliance‑oriented environments (security controls, auditability, privacy, sensitive financial or personal data handling).
• Strong engineering fundamentals including design patterns, separation of concerns, scalable architecture, and pragmatic trade‑offs—with attention to accuracy and reconciliation in calculation‑heavy systems.
• Experience with agentic or AI‑assisted development workflows such as spec‑driven development, agent‑driven development using tools like Claude Code or Codex, or similar AI coding agent practices.
• Demonstrated ability to build products that incorporate AI capabilities including prompt design, LLM API integration, or AI‑augmented user experiences.

Preferred Qualifications

• Direct experience building or integrating with payroll, shadow payroll, compensation collection, equity administration, or global mobility tax platforms.
• Familiarity with cross‑border compensation concepts: gross‑to‑net calculations, hypothetical tax, tax equalization, modified shadow payroll, and equity‑related compensation events (RSU vest, ISO/NSO exercise, ESPP).
• Experience integrating with HCM, payroll, and equity systems such as Workday, SAP SuccessFactors, ADP, Ceridian/Dayforce, Shareworks, E*TRADE, Carta, or country‑specific payroll engines.
• Azure certifications and/or Microsoft certifications.
• Experience with event‑based and distributed systems including messaging and asynchronous workflows for payroll cycles and equity event processing.
• Data and persistence experience with SQL Server and ORMs (Entity Framework, nHibernate) plus caching strategies; experience modeling compensation, payroll, and equity data is a strong plus.
• Strong testing discipline including TDD and BDD, xUnit, Jest or Mocha, CI/CD automation, and quality gates—especially for calculation engines requiring reconciliation and regression coverage.
• Experience building analytics and reporting with BI and data visualization tools, including payroll reconciliation, compensation analytics, and equity reporting.
• Exposure to mobile ecosystems (iOS and Android) and API design supporting mobile clients for assignee/employee experiences.
• Experience with prompt engineering patterns, RAG architectures, vector databases, or AI orchestration frameworks (e.g., LangChain, Semantic Kernel, Azure AI Services).
• Familiarity with AI code generation and review workflows, including evaluating and curating AI‑generated code for production readiness in regulated financial workflows.

Technical Skills We Value

• Frontend: Next.js, React, TypeScript, HTML, CSS, SPA architecture, performance and accessibility.
• Backend: C#, ASP.NET, WebAPI, RESTful design, authentication and authorization patterns, high‑integrity calculation services.
• Cloud: Azure PaaS services, observability, secure networking, identity, deployment automation.
• Domain: Compensation Collection workflows, Shadow Payroll calculation and reporting, Equity event processing and tax treatment, cross‑border payroll integrations.
• Engineering practices: Git‑based workflows, secure SDLC, spec‑driven development, AI‑assisted code reviews, automated testing, reconciliation tooling, documentation.
• AI‑enabled delivery: agentic development using Claude Code, Codex, or similar AI coding agents; spec‑driven development workflows; prompt engineering; LLM API integration; RAG patterns; AI orchestration frameworks; responsible AI practices and observability.

What Success Looks Like

• Delivers complex Compensation Collection, Shadow Payroll, and Equity features end‑to‑end with high quality, predictable timelines, and production readiness aligned to payroll cycles and equity event deadlines.
• Produces clean, maintainable code—whether hand‑written or AI‑generated—with strong test coverage, reconciliation checks, and clear documentation.
• Identifies and resolves performance, reliability, accuracy, and security issues before they reach production or affect a client’s payroll or equity event.
• Contributes meaningfully to architecture and raises standards through code reviews and technical leadership across the compensation, payroll, and equity domains.
• Communicates clearly with engineering, product, and domain experts; flags risks early; and collaborates effectively across teams and geographies.
• Effectively leverages agentic development tools and AI‑augmented workflows to increase velocity while maintaining the quality, accuracy, and security standards required for regulated financial workflows.

Education

Bachelor’s degree in computer science, Engineering, or related field required. Master’s degree preferred.

Why This Role

You’ll help build and scale the technology behind Compensation Collection, Shadow Payroll, and Equity—the engines that keep globally mobile employees of the world’s largest multinationals paid accurately, taxed correctly, and compliant across dozens of jurisdictions. You’ll modernize and operate a platform that sits at the intersection of complex tax regulations, sensitive financial and personal data, and high‑stakes global payroll and equity events. You’ll also work at the forefront of AI‑augmented engineering, using agentic development practices and building AI‑powered product experiences that redefine how global mobility compensation, payroll, and equity technology is delivered. We are an equal opportunity employer that does not discriminate on the basis of any legally protected status. Please note, AI is used as part of the application process.