I work mostly on systems that other people's work depends on once they ship — scalable e-commerce platforms, supply chain systems and SaaS applications. The recurring problem across all of them is the same one: take something that behaves for a handful of users and make it hold up as production-ready software.
In practice that means full-stack ownership rather than a narrow slice — PostgreSQL database design and the query paths that hang off it, React and Next.js at the front, and CI/CD pipeline automation so that releasing is uneventful. On the platform I worked on at APP360 that reached 80,000+ users, with performance optimisation measured at 40–65%.
I pay attention to the parts that are easy to skip: reusable component libraries, access control that is actually enforced by middleware rather than by convention, and documented releases. Most of what I have shipped went out as 55+ incremental builds with release notes, not as one large launch.