Fullstack Senior Software Engineer (TypeScript, C#, React, AWS)

2 Vacancies: 1 x Permanent Hire 1 x Maternity Leave Cover - Fixed Term Employee for 12 months Logistics: Hybrid - 2 days per week in our London HQ Alto Software Group is a B2B SaaS company that powers more than half of all UK housing transactions each year. We create software solutions that connect businesses and consumers, delivering a one-stop shop for estate agents and home builders. Our goal is to drive efficiency, speed up transactions, reduce risk, and improve the end-customer experience. Our platform is built on a proven C# and .NET foundation, and we're building what comes next on top of it. That means new frontier AI capabilities in TypeScript, sitting alongside a C# estate we're actively evolving for the next era. The interesting challenge isn't just being productive in both stacks, it's knowing when each is the right tool and keeping the whole system coherent as our product grows. If you are passionate about how software should be built and want to be in the room where those decisions get made, there's never been a better time to join us. What You'll Do Identify the right problems to solve across a dual-stack C# and TypeScript backend, being intentional about choosing the right tool for the job. Implement microfrontend web applications in React and TypeScript, with an eye for component design and the UX implications of what you build. Take end-to-end ownership of features from early design through to production. You're in the product conversation from the start, move fast from idea to working prototype to learn what's worth building, and see it through to delivery. Work closely with our product team and engage customers to understand the problems worth solving, bringing that perspective back into how you design and build. Work with AWS managed services including ECS/Fargate, Lambda, SQS, DynamoDB, and DocumentDB to build and evolve a scalable, event-driven architecture that performs under real load. Use AI coding agents (e.g. Claude Code, Cursor) to accelerate delivery and embody a genuine shift in how you design, implement and review code Set a high bar for craft and collaboration, from well-considered architecture decisions to clear pull requests, thorough testing, and feedback that levels up the people around you. Help shape how we build, not just what we build. Exploring how AI can remove repetitive toil and tighten feedback loops so we spend our energy on the problems worth solving. Our Technology Stack We believe in using the right tool for the job. Our current stack includes: Backend: TypeScript, Node.js, C#, .NET Frontend: TypeScript, React Cloud & Infrastructure: AWS (ECS, Lambda, SQS, DocumentDB, DynamoDB), Terraform, SST (Infrastructure as Code) Architecture: Microservices, Microfrontends, Event-driven architecture What You Need to Be Successful A strong background in TypeScript and C# with experience building modern, production-grade APIs and distributed systems. Proven experience with asynchronous, event-driven architecture and hands-on familiarity with AWS managed services including ECS/Fargate, Lambda, SQS, DynamoDB, and DocumentDB. Real-world experience with AI coding agents and genuine opinions about where they help, where they fall short, and where things are heading. You're actively experimenting with how agentic AI can remove friction from the software delivery lifecycle and create better product experiences. You think like a product engineer, not just a software engineer. Driven by the value a feature creates rather than the mechanics of how it's built, and grounded in evidence to understand what customers actually need. Comfortable with ambiguity and early-stage work. You prototype to learn and get feedback, and you adapt quickly when the picture changes. Pragmatic about trade-offs. You can balance speed and depth, manage technical debt strategically, and make the call on when good enough ships and when it needs more. A collaborator who raises the bar around them, through clear communication, well-written proposals, actionable feedback, and a willingness to do the unglamorous work that keeps a codebase healthy. We are committed to building a diverse and inclusive team and welcome applications from all backgrounds. If you have a strong foundation in TypeScript or C# and everything above sounds like the way you already think, we'd love to hear from you. Everyday Flex - greater flexibility over where and when you work 25 days annual leave + extra days for years of service Day off for volunteering & Digital detox day Festive Closure - business closed for period between Christmas and New Year Cycle to work and electric car schemes Free Calm App membership Enhanced Parental leave Fertility Treatment Financial Support Group Income Protection and private medical insurance Gym on-site in London 7.5% pension contribution by the company Discretionary annual bonus up to 10% of base salary Talent referral bonus up to £5K We want to make ASG more welcoming, fair and representative every day. We’ll consider everyone who applies for this role in the same way, regardless of your ethnicity, colour, national origin, religion, sexual orientation, gender, gender identity, age, physical disability, neurodiversity status, family or parental status, or how long you’ve spent unemployed.