Attendify—Classroom Attendance App

Role & context

1. 01

   Multi-tenant ownership isolation

   every class/student/attendance query is scoped by ownerId from the JWT, so one teacher can never read or mutate another's data

2. 02

   Idempotent writes

   a composite unique index (studentId, date) plus an upsert path means the same mark sent twice never creates duplicates

3. 03

   Password hygiene

   bcrypt-hashed passwords and a sanitize() projection that strips the hash before any user object leaves the API; password reset requires the old password

4. 04

   Hook-per-screen separation of concerns

   each screen has a sibling use<Screen>.tsx owning data/effects, leaving the screen file as pure JSX

5. 05

   Cache-correctness over manual refetch

   RTK Query tags drive invalidation, so marking a student auto-refreshes dependent summary screens

6. 06

   End-to-end type safety

   TypeScript strict, @/* path aliases, and Expo Router typed routes from route name to API call to Redux state

• School reports demand boys/girls splits at four granularities (daily, weekly, monthly, yearly), and the academic 'week' is week-within-the-month (1-5), not ISO week — naive per-endpoint SQL would be four near-duplicate queries disagreeing on edge cases.

  FixCentralised the maths in the attendance service: fetch the marks for the date range once, then group in-memory by a custom week-of-month function and by gender. One source of truth feeds all summary endpoints with render-ready totals.

• On Android cold start, the login screen flashed before redux-persist rehydrated the saved JWT.

  FixWrapped the app in PersistGate (whitelist: auth) and gated the entry route on the rehydrated accessToken before choosing login vs class-select; auth routes also suppress the bottom-tab layout.