Lead Full Stack Engineer

Lead Full Stack Engineer, employed by Nexifi and embedded full-time with one of our enterprise clients. You will work inside the client's delivery team on a high-volume, consumer-facing registration and payments platform. This is a hands-on Builder / Tech Lead role, not an advisory one. At Nexifi, we focus on outcomes that matter. Our culture is built on trust, transparency, collaboration and strong technical delivery. We work as a genuine extension of our clients’ teams, taking ownership of complex challenges and adapting as priorities evolve. You will join experienced practitioners who value practical thinking, continuous improvement and delivering work that creates measurable impact. This is a flexible role with a preference for candidates in or near Sydney NSW, but exceptional candidates may be considered for fully remote work. Key Technologies TypeScriptReactNode.jsAWS LambdaAmazon API GatewayAWS CDK and infrastructure as codeRelational databases and SQL Responsibilities Design, build, and ship features end-to-end across the frontend, backend and supporting infrastructure.Own work through its full lifecycle, from technical discovery and implementation through testing, deployment and post-release verification.Provide technical leadership while remaining hands-on, helping engineers make sound design and implementation decisions.Write and review technical designs for changes that cross service or team boundaries, incorporating feedback from relevant stakeholders.Diagnose production issues in a live platform supporting real users and financial transactions, including tracing failures across applications, services, databases, queues and external integrations.Contribute to platform health work: cost reduction, decommissioning unused resources, dependency upgrades, and reducing operational noise.Participate in code review as both author and reviewer, and hold a consistent quality bar.Test the code you ship. Work alongside a dedicated QA function rather than in place of it.Work directly with the client’s product owners, QA engineers, architects and engineering teams, representing Nexifi credibly and professionally.Keep documentation current for the parts of the system you touch. Must have Strong commercial TypeScript experience across frontend and backend development, including production experience with Node.js.Deep React expertise, including component architecture, performance optimisation, rendering behaviour and diagnosing complex state-management issues.Demonstrated experience leading technical delivery while remaining an active contributor to the codebase.Solid relational database skills: schema design, query performance, migrations, and understanding what a change does under load.Production AWS experience, including managed services, IAM, security, observability, operational support and cost management.Hands-on experience building serverless applications using AWS Lambda and API Gateway, including their operational and architectural patterns.Infrastructure-as-code experience using AWS CDK or a comparable framework. Able to make infrastructure changes safely and understand how to identify and manage resources inside and outside IaC control.Experience designing and operating asynchronous and event-driven systems, including queues, topics, retries, dead-letter queues, idempotency, ordering, duplicate delivery and partial consumer failure.Experience using AI coding agents such as Claude Code, Open Code or Copilot to accelerate software delivery, including codebase exploration, implementation, testing, refactoring and documentation. While applying sound engineering judgement, verifying generated outputs and remaining accountable for the quality and security of all delivered code.