Quick context: I'm the technical co-founder at an AI focus-group moderation startup (voice-based, live multi-participant — think a research platform, not a chatbot). This is actually my first hands-on build. I spent 15+ years as a Petroleum Engineer before doing a Master's in Applied AI, and while the program was great for the ML/AI side, it didn't cover much in the way of software engineering fundamentals or system design — so a lot of this is me learning architecture by doing, in real time, on a live product. I've been heads-down on the actual moderation engine (LiveKit + STT/TTS + an AI avatar) and just finished a client-facing frontend for my non-technical co-founders using Claude Design. Now I'm at the classic solo-founder fork: the frontend looks real, the backend (FastAPI + Postgres) is running but mostly unwired, and I'm trying to figure out the right order of operations before I just start bolting things together. Specifically wrestling with: 1. Auth-first vs. feature-first. Nothing downstream — user records, engagement data, analytics — means anything until real auth exists. Feels obvious in hindsight, but it means the "foundation" work is invisible to stakeholders who just want to see features ship. 2. What to actually track. I want to know where users drop off in a multi-step workflow (signup → contract → study setup → audience → instrument → session → report) without over-engineering a custom analytics stack before I even have real users. Self-hosted PostHog vs. just a Postgres events table vs. something else? 3. How much "systems design" to front-load. I'm working through Designing Data-Intensive Applications and the System Design Interview books to make better architecture calls now instead of paying for them later — but at 10 hrs/week solo, I can't read either cover to cover before shipping. Curious how others have picked their battles here (I landed on: data modeling + transactions + event/stream processing chapters now, replication/partitioning/consensus later).