Product Requirements Document (PRD): LevainLog

1. Executive Summary

LevainLog is a high-performance, mobile-first sourdough starter management system designed for the 2026 baking ecosystem. It bridges the gap between traditional artisanal baking and data-driven precision by allowing users to track feeding schedules, environmental variables (temperature/humidity), and fermentation milestones. Utilizing a local-first architecture and high-fidelity charting, LevainLog ensures bakers can maintain starter health even in low-connectivity environments like professional kitchens or basements.

2. Problem Statement

Maintaining a sourdough starter is a delicate balance of biology and environmental science. Home bakers and professionals often struggle with:

Inconsistency: Forgetting feeding times or ratios leads to weak yeast activity.
Environmental Blindness: Failing to account for how ambient temperature affects rise time.
Troubleshooting Fatigue: Difficulty in identifying if a starter is sluggish, hungry, or contaminated (mold/hooch).
Data Fragmentation: Using disparate notebooks or photo galleries that lack actionable insights.

3. Goals & Success Metrics

Business Goals

Establish LevainLog as the primary utility for the fermentation community.
Achieve a high retention rate through utility-based push notifications.
Minimize support overhead by providing automated troubleshooting tools.

Success Metrics

Monthly Active Users (MAU): Aim for 50,000 within the first year.
Log Completion Rate: Percentage of users who log at least 4 consecutive feedings.
Notification Engagement: >40% click-through rate on feeding reminders.
Offline Resilience: <1% data loss reported during offline-to-online transitions.

4. User Personas

5. User Stories

As a baker, I want to log the exact weight of flour and water so I can maintain a consistent 100% hydration starter.
As a home cook, I want to receive a notification when my starter is likely at its peak so I can start my autolyse on time.
As a user in a basement kitchen, I want to log my feeding data offline so that I don't lose progress when Wi-Fi is unavailable.
As a micro-bakery owner, I want to compare rise times against ambient temperature to adjust my bulk fermentation schedule.
As a concerned baker, I want to compare my starter's surface to a gallery of healthy vs. moldy starters to ensure food safety.

6. Functional Requirements

6.1 Starter Management

Multi-Starter Support: Create profiles with Name, Flour Type (Rye, Whole Wheat, AP), and Creation Date.
Hydration Calculator: Automatically calculate and store hydration % based on input weights.

6.2 Feeding Log & Reminders

Dynamic Logging: Input fields for Starter Carryover, Flour Weight, and Water Weight.
Environmental Auto-fill: Integration with OpenWeather API to pull ambient temp/humidity based on location.
Smart Notifications: Using Notifee to schedule the next feeding reminder based on user-defined intervals (e.g., 12h or 24h).

6.3 Rise Tracker & Visual Diary

Milestone Marking: Buttons to mark "Fed," "Doubled," "Peak," and "Collapsed."
Image Capture: Native camera integration to store high-res photos of bubble structure.
WebP Compression: Automatic client-side conversion to WebP for efficient S3 storage.

6.4 Health Dashboard

Trend Visualization: Dual-axis charts showing "Rise Time to Peak" vs. "Ambient Temperature."
Statistical Averages: Calculation of average time-to-peak over the last 7 days.

7. Technical Requirements

7.1 Tech Stack (2026 Standards)

Frontend: React Native v0.83.x (New Architecture / Hermes).
Language: TypeScript v5.9.3.
Backend: Node.js v25.3.0 with Express v5.2.1.
Database & ORM: PostgreSQL (v17+) with Prisma v7.2.0 (ESM-first).
Local Database: expo-sqlite with Prisma Client for React Native.
Synchronization: PowerSync (Local-first architecture for offline resilience).
Auth: Firebase Authentication with OAuth 2.0 (Google/Apple).
Storage: AWS S3 with Transfer Acceleration and Signed URLs.

7.2 Integrations

OpenWeather One Call API 3.0: For historical and real-time climate data.
Notifee: For advanced background notification scheduling.
React Native Gifted Charts: For dual-axis time-series visualization.

8. Data Model

8.1 User

id: UUID (Primary Key)
email: String (Unique)
unit_system: Enum (Metric/Imperial)
created_at: Timestamp

8.2 Starter

id: UUID
user_id: FK -> User.id
name: String
flour_type: String
base_hydration: Float
is_active: Boolean

8.3 FeedingEvent

id: UUID
starter_id: FK -> Starter.id
timestamp: Timestamp
flour_weight: Float
water_weight: Float
carryover_weight: Float
ambient_temp: Float
humidity: Float
photo_url: String (S3 Path)

8.4 RiseMetric

id: UUID
feeding_id: FK -> FeedingEvent.id
peak_time: Timestamp
peak_height_ratio: Float (e.g., 2.0 for doubled)
notes: Text

9. API Specification (Simplified)

`POST /api/v1/feedings`

Auth: Required (Firebase JWT)
Body: { starter_id, flour, water, carryover, temp, humidity }
Response: 201 Created with feeding object.

`GET /api/v1/storage/upload-url`

Purpose: Requests a pre-signed S3 URL for image upload.
Query Params: fileName, contentType.
Response: { uploadUrl, fileKey }.

`GET /api/v1/analytics/trends/{starter_id}`

Response: Array of feeding events with associated rise metrics for charting.

10. UI/UX Requirements

Dashboard: A "Current Status" card showing the time elapsed since the last feeding and a countdown to the next.
Quick Action Button (FAB): Central "+" button to log a feeding or a rise milestone.
Chart Interaction: Users can "scrub" (long-press and slide) across the rise chart to see specific data points.
Dark Mode: Native support for 2026 OS-level dark/light switching.
Haptic Feedback: Subtle vibrations when weights are logged or milestones are hit.

11. Non-Functional Requirements

Performance: UI must maintain 120fps on supported devices using React Native Skia for charts.
Security: All photos must be private; access only via 15-minute expiration Signed URLs.
Offline-First: All data must be writeable while offline and sync automatically via PowerSync LSN (Log Sequence Numbers).
Accessibility: Support for dynamic font sizing and a minimum contrast ratio of 4.5:1.

12. Out of Scope

Recipe Book: This version will not store full bread recipes, only starter-related data.
Social Network: No public user profiles or comments in v1.
E-commerce: No selling of starters or baking kits.

13. Risks & Mitigations

14. Implementation Tasks

Phase 1: Project Setup

[ ] Initialize project with React Native 0.83.x and TypeScript 5.9.3
[ ] Configure ESLint and Prettier for "Strict" TS 7-readiness
[ ] Set up Firebase Project and Native Auth SDK
[ ] Initialize Prisma 7.2.0 with PostgreSQL and expo-sqlite adapter

Phase 2: Core Data & Offline Sync

[ ] Define Prisma Schema for Starters and Feeding Events
[ ] Implement PowerSync / ElectricSQL sync bridge for Local-First persistence
[ ] Build "Add Starter" wizard UI
[ ] Implement Offline Outbox pattern for feeding logs

Phase 3: Feeding Logic & Notifications

[ ] Create Feeding Log form with hydration calculator
[ ] Integrate OpenWeather One Call 3.0 for auto-filling climate metadata
[ ] Implement Notifee for dynamic reminder scheduling
[ ] Build background task to reschedule reminders when a feed is logged early

Phase 4: Visuals & Analytics

[ ] Integrate react-native-compressor for WebP conversion
[ ] Implement S3 Pre-signed URL flow via Node.js v25 backend
[ ] Build Health Dashboard using React Native Gifted Charts (Dual-Axis)
[ ] Create photo gallery with lazy loading for historical visual diary

Phase 5: Troubleshooting & Polish

[ ] Implement "Health Check" reference gallery (Healthy vs. Moldy)
[ ] Add Haptic Feedback and Reanimated 4 transitions
[ ] Conduct final performance audit (120Hz check on Skia components)
[ ] Beta test with "Scientist Sam" persona group