Senior Full Stack Engineer

SundaySky; York and North Yorkshire; On-site; GBP 75,000 - 110,000; Full time

Job summary

SundaySky in York, UK is seeking a Senior Full-Stack Engineer who can independently design, build, test, and operate complex capabilities across our web app, backend services, data integrations, and video creation platform.

You will own product capabilities from discovery to production deployment, translate requirements into scalable technical solutions, and mentor peers while partnering with Product, UX, QA, and DevOps.

Qualifications

• Experience designing scalable SaaS applications.
• Proficient in React and modern JS/TS.
• Strong backend and API design capabilities.

Responsibilities

• Design and implement end-to-end product capabilities across frontend, backend, and data integrations.
• Lead technical design of complex initiatives and break them into executable components.
• Write automated tests and contribute to code reviews and quality practices.
• Collaborate with Product, UX, QA, and DevOps throughout delivery.

Skills

Full-stack development

React

Node.js

TypeScript

AWS

REST APIs

Git

PostgreSQL

Docker

Tools

Git

PostgreSQL

Docker

Job description

• We are seeking a Senior Full-Stack Engineer who can independently design, build, test, and operate complex capabilities across our web application, backend services, data integrations, and video creation platform
• This is a hands-on individual-contributor role for an engineer who can take ownership of significant product capabilities from technical discovery through production deployment
• This person should be able to work from product requirements and design concepts, identify technical gaps and edge cases, propose an implementation approach, and deliver production-quality software with limited oversight
• Design and implement end-to-end product capabilities spanning frontend applications, backend services, APIs, databases, and third-party integrations
• Translate product requirements, UX designs, and acceptance criteria into scalable technical solutions
• Lead the technical design of moderately complex and complex initiatives
• Break large capabilities into executable technical components and development increments
• Develop responsive, accessible, and maintainable user interfaces using modern JavaScript and TypeScript frameworks
• Design and implement backend services, application APIs, business logic, data models, and asynchronous workflows
• Build and maintain integrations with enterprise platforms, data sources, AI services, media providers, and other third-party systems
• Contribute to video creation, rendering, personalization, animation, asset management, analytics, and distribution capabilities
• Identify performance, scalability, reliability, security, and maintainability concerns before they become production issues
• Write automated unit, integration, component, and end-to-end tests
• Participate in code reviews and establish strong patterns for code quality and engineering consistency
• Diagnose and resolve complex production issues across application and infrastructure layers
• Improve observability through structured logging, monitoring, metrics, tracing, and actionable alerts
• Partner closely with Product, UX, QA, DevOps, and other engineers throughout the delivery lifecycle
• Mentor mid-level engineers through technical guidance, code reviews, pairing, and constructive feedback
• Contribute to architectural standards, engineering practices, shared components, and reusable platform capabilities
• Use AI-assisted engineering tools responsibly to accelerate development, testing, documentation, troubleshooting, and code modernization
• Participate in release readiness, production support, incident response, and root-cause analysis

Communicate risks early and propose practical alternativesIdentify missing requirements, edge cases, dependencies, and operational concernsDeliver maintainable solutions rather than narrowly solving the immediate ticketOwn a complex capability with limited technical supervisionStrong full-stack development experience with modern JavaScript and TypeScriptAdvanced experience with a modern frontend framework, preferably ReactThe ideal candidate combines strong frontend and backend expertise with sound architectural judgment, product thinking, and the ability to raise the technical performance of the broader teamStrong understanding of automated testing strategies at the unit, integration, API, component, and end-to-end levelsStrong understanding of software design principles, modular architecture, scalability, technical debt management, and maintainabilityWorking knowledge of application security, authorization, identity, secrets management, data protection, and secure coding practicesStrong understanding of cloud-native application development, preferably within AWSExperience with containers, CI/CD pipelines, infrastructure environments, and modern deployment practicesStrong backend development experience using Node.js, Python, Java, C#, or a comparable server-side technologyExperience building complex, workflow-oriented web applications rather than primarily content-oriented websites7+ years of professional software development experience, including substantial experience building production SaaS applicationsExperience integrating with third-party APIs, authentication providers, data platforms, or enterprise systemsExperience designing and implementing REST APIs, event-driven services, background jobs, and asynchronous workflowsStrong understanding of relational and non-relational data modelingExperience diagnosing distributed application issues using logs, metrics, traces, database analysis, and browser toolingExperience working with Git-based development workflows, pull requests, code reviews, branching strategies, and automated quality checksStrong knowledge of component architecture, state management, frontend performance, responsive design, and browser behaviorExperience with PostgreSQL or another modern relational databaseProduce implementation plans that other engineers can executeA successful Senior Full-Stack Engineer should be able to:Make sound technical tradeoffs and clearly explain the reasoning behind themDemonstrate accountability for the production behavior of the software they buildBalance speed, quality, scalability, and technical debtImprove the quality and productivity of engineers around themDebug issues that span multiple services or application layersExperience with message queues, event buses, serverless services, or distributed job-processing systemsExperience improving or modernizing an established software platform while continuing to deliver new product capabilitiesExperience in a multi-tenant SaaS environmentExperience with AI platforms, large language models, retrieval-augmented generation, prompt orchestration, or AI-generated mediaExperience with browser-based motion graphics using React, JavaScript, CSS animations, Canvas, WebGL, or related technologiesExperience building configurable enterprise platforms with permissions, approval workflows, auditability, and governance controlsExperience with video, audio, media processing, creative tooling, animation, rendering, or digital asset managementExperience with infrastructure as code and production observability platforms