Structured post-launch development based on actual usage rather than continued assumption. Product analytics instrumented from day one using PostHog (self-hosted or cloud) or Mixpanel: funnel analysis to identify where users drop off (the 40% who complete signup but never return usually drop at a specific feature that doesn't work as expected), feature adoption heatmaps, and cohort retention curves that show whether different user segments retain differently. Error monitoring via Sentry configured at launch with source maps and release tracking -- so every uncaught exception is attributed to a specific commit, user session, and code path rather than surfacing as a vague support ticket. Feature flags via LaunchDarkly or Unleash enable controlled rollout of second-phase features to a percentage of users before full release, and allow instant kill-switch without a deployment if a new feature causes unexpected behaviour in production. Feature requests from early customers categorised by frequency, revenue impact, and implementation cost -- not everything the loudest customer asks for is worth building. Architecture review against the next-phase requirements: the decisions appropriate for an MVP (simple queue instead of Kafka, single-process deployment instead of microservices) may not hold at 10x the user count; the review identifies which ones need replacing before they constrain growth. For founders approaching seed funding, we prepare the architecture documentation, codebase handoff package, and metrics export that technical due diligence teams ask for: database schema, API documentation, infrastructure diagram, test coverage report, and the dependency audit showing no critical CVEs. Second phase scoped and priced as a separate fixed-cost engagement based on what the data shows rather than what was anticipated at the start.