# Lesson 4 complete (deal-breakers)

Learner finished lesson 4 with **all quiz answers correct**. Demonstrated design-review scan: wrong-tool redirects (IDB / Cache / pickers / multi-device truth), private ≠ user-visible FS, best-effort quota/eviction, exclusive lock ownership, heavy I/O via dedicated worker. External primaries still deferred (lesson-first path). Next ZPD: decision playbook synthesis — four gates + full briefs; track complete after lesson 5.