NullStack engineers web and mobile platforms where Core Web Vitals scores are acceptance criteria, not aspirational benchmarks: a project does not close until the field data in Google Search Console confirms LCP under 2.5 seconds, INP under 200 milliseconds, and CLS under 0.1. This standard is enforced in code, not in a post-launch optimisation retainer. Our backend architecture uses Django REST Framework to build decoupled, API-first systems  meaning the frontend, mobile app, and any future integrations consume the same data layer without duplication. Flutter gives us a single codebase for iOS and Android that reduces ongoing maintenance overhead by approximately 40 percent compared to maintaining two native codebases, a figure we track per client through post-launch sprint cost analysis. For security-sensitive platforms, we implement role-based access control, end-to-end TLS, and comprehensive audit logging as baseline features not premium add-ons. A hospital client portal launched in early 2025 passed a third-party VAPT audit with zero critical findings on first submission. Our design process treats mobile as the primary experience and desktop as the extension not the reverse.