Senior Full Stack Engineer

Senior Full Stack Engineer | AI SaaS | TypeScript, Node.js, React, GraphQL, AWS London hybrid, Few days per month in office | Up to £120,000A well-funded AI SaaS company is hiring a Senior Full Stack Engineer to help build a platform used by governance, risk and compliance teams to automate complex operational workflows.The product sits across evidence collection, compliance workflows, customer integrations, permissions, audit trails, reporting, data validation and AI-assisted automation. It needs engineers who can think beyond feature tickets and understand how product decisions, backend design and production reliability connect.The strongest fit is a backend-leaning full stack engineer who can own a feature from product problem through to technical design, implementation, failure handling and release.You should be comfortable building in React, but the heavier technical bar is around TypeScript, Node.js, GraphQL, AWS, async workflows, third-party integrations and reliable SaaS architecture.What you’ll be working onYou’ll be building product features where the complexity sits underneath the UI: data moving between systems, background jobs running reliably, customer workflows staying accurate, external APIs failing safely, and users needing clear visibility into what is happening.The work will include:• Building full stack product features using TypeScript, Node.js, React, GraphQL and AWS • Designing backend services that support workflow automation, evidence collection and compliance operations • Working with queues, background jobs, retries, idempotency, dead-letter handling and async processing • Building integrations with customer systems and third-party APIs where reliability, error handling and observability matter • Designing for multi-tenant SaaS environments, including tenant boundaries, permissions, data integrity and workflow fairness • Creating React product experiences that reflect real backend state, including pending, failed, retrying and completed workflow states • Improving system visibility through structured logging, metrics, tracing, alerts and production diagnostics • Helping shape technical decisions around architecture, delivery speed, maintainability and operational risk • Using AI thoughtfully across product capability and engineering workflowWhat the role needsStrong candidates will have evidence of owning difficult engineering problems in production, not just contributing to isolated tickets.You should bring:• Strong TypeScript and Node.js experience in commercial product environments • Solid React experience, ideally building real workflow-heavy product interfaces • GraphQL experience, including API design and data modelling considerations • AWS experience across services such as Lambda, SQS, SNS, DynamoDB, EventBridge, Step Functions, ECS or similar • Experience designing async workflows, queues, workers, retries, backoff strategies, idempotency and DLQs • Experience integrating with external APIs, customer platforms, SaaS tools or third-party data sources • Strong understanding of production failure modes: slow APIs, duplicate events, bad payloads, rate limits, partial failures and data inconsistency • Ability to explain system design decisions clearly, including trade-offs, constraints and why one approach was chosen over another • Product ownership mindset, with the ability to connect technical choices back to user impact and business workflow • Comfort working in a small, senior engineering team where ownership is high and ambiguity is normalThe levelThis is a senior engineering role for someone who can explain work in terms of:Problem, design, trade-offs, failure handling and outcome.Examples of relevant experience could include:• Designing a queue or worker system where one customer cannot block everyone else • Building a payment, checkout, compliance, reporting or workflow system where accuracy matters • Integrating unreliable third-party APIs and protecting the product from their failure modes • Owning a GraphQL/API layer that simplifies complex underlying systems • Building React interfaces that accurately show async workflow state • Improving reliability, observability or data integrity in a production SaaS platform • Taking ownership of a feature area rather than only completing assigned ticketsBackground in GRC, RegTech, security, compliance, fintech, payments, workflow automation or enterprise B2B SaaS would be useful. The core requirement is proven product engineering depth across full stack delivery and backend reliability.Package• Up to £120,000 • London hybrid, around 1 day per month in office • Senior engineering role in a well-funded AI SaaS business • Modern TypeScript, Node.js, React, GraphQL and AWS stack • High ownership across product, architecture and implementation • Complex workflow, integration and reliability problems • Small engineering team with strong technical influenceThis suits someone who wants meaningful ownership of difficult product engineering problems and can operate as a hands-on senior engineer across frontend, backend, architecture and production reliability.