Senior Full-Stack Software Engineer

This Senior Software Engineer role in Sydney CBD is a full-stack C#/.NET and React opportunity paying a $180K–$200K package. Spring is almost here, so maybe it's time to warm up your career too. We're working with a fast-growing fintech exchange operating across crypto and FX, building high-performance digital products used by customers across multiple markets. They're after a Senior Software Engineer who can genuinely work across the stack: strong C#/.NET engineering on the backend, coupled with hands-on React and TypeScript capability on the frontend. This isn't a backend role where you occasionally tweak a React component. You'll own customer-facing features end-to-end, contribute to architecture, and help shape the engineering standards behind a platform where speed, reliability, conversion and user experience genuinely matter. What you'll be doing as a Senior Software Engineer Build and maintain features across the customer-facing product including the website, onboarding, account creation, promotions and authentication journeysDevelop backend APIs and services using C# / .NETBuild modern frontend experiences using React.js and TypeScriptTake ownership of features from solution design through development, release and production supportContribute to architectural decisions and technical direction within the engineering squadWrite clean, readable, testable and maintainable codeSet a high standard through thoughtful code reviews and engineering best practiceImprove frontend performance, accessibility, SEO and overall customer experienceBuild and maintain multi-region and multi-language product experiencesWork with internationalisation and localisation including i18n, l10n and routing strategiesIdentify and resolve performance, reliability and quality issues before they become problemsWork closely with product, marketing and commercial teams on technology that directly influences customer acquisition and growth What we look for in a Senior Software Engineer You're Likely An Experienced Senior Full Stack Engineer Who Is Comfortable Taking Responsibility Rather Than Waiting For Perfectly Defined Tickets. You'll Bring Strong commercial C# / .NET backend engineering experienceSolid hands-on React.js / TypeScript development capabilityExperience building and shipping customer-facing digital productsStrong API and service development experienceExperience with headless CMS and content-driven architecturesUnderstanding of scalable, maintainable frontend architectureExperience building multi-region / multi-lingual productsKnowledge of i18n and l10nStrong understanding of technical SEO including crawlability, structured data and Core Web VitalsGood engineering instincts around edge cases, failure modes, testing and maintainabilityAn eye for frontend quality, usability and conversion, not simply whether something technically worksA genuine ownership mentality: you care what happens after the code reaches productionConfidence working in an environment where priorities can move quickly Nice to have Fintech, crypto, FX, trading or exchange experienceExperience with high-conversion consumer or e-commerce productsCustomer onboarding or identity verification flows, including KYCSSO and authentication technologies including OAuth 2.0, OIDC or SAMLStrong frontend performance knowledge including Lighthouse, accessibility and cross-device optimisation Why this Senior Software Engineer role This is a senior engineering role with real product ownership. You'll be working on technology sitting directly between the business and its customers, rather than disappearing into an internal platform team three layers removed from the product. You'll have the opportunity to influence architecture, engineering quality and technical direction while remaining hands-on. The business is growing, the product is evolving quickly, and there's plenty left to build. The offer $180,000 base plus superannuation plus bonusPackage up to approximately $200,000Sydney CBD, five days per week onsitePermanent position with real product ownershipFast-moving fintech environment Please note: this position is Sydney-based and requires full Australian working rights. Sponsorship is not available. If you're a strong C#/.NET and React engineer who enjoys building products people actually use, this could be a very good way to head into spring. Apply now or reach out for a confidential chat. About This Senior Software Engineer Role Big Wave Digital has placed engineers into product teams across Sydney for well over a decade, so we can tell you what the team is actually like before you interview. If you are weighing up a move, we will be honest about the tech, the people and the trade-offs rather than selling you a job description. You can also browse our other technology jobs in Sydney, and if you want to sharpen up before interviewing, the official Microsoft .NET documentation is a solid refresher. Apply now if this Senior Software Engineer position is the step you have been waiting for, and we will come back to you quickly with real feedback either way.