Project YAKAP-Link: The "Local-First" Pharmaceutical Logistics Grid

Status: Technical Proposal / Proof of Concept Core Philosophy: "Equity through Engineering" — Solving the Last Mile connectivity gap in Philippine healthcare.

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1. Executive Summary

The Problem: PhilHealth's YAKAP/GAMOT mandates require Rural Health Units (RHUs) to submit real-time inventory and dispensing logs. However, Class 4-5 municipalities suffer from intermittent connectivity. Current "Cloud-Only" EMRs fail in these environments, leading to:

1. Data Gaps: Encoding backlogs when the internet is down.
2. Stockouts & Waste: Medicine expires in one clinic while a neighboring town is in critical shortage, due to a lack of visibility.

The Solution: YAKAP-Link is a Local-First Progressive Web App (PWA). It treats the local device as the primary source of truth, ensuring 100% uptime for dispensing. It implements a "Mesh Redistribution Engine" that mathematically identifies and prevents waste before it happens.

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2. System Architecture

2.1 The "Offline-First" Core (ADR-001)

Unlike traditional web apps that read from a server, YAKAP-Link reads from the device's internal storage (IndexedDB).

• Write Path: Dispensing actions are written immediately to the local Ledger. The UI never "loads"; it is instant.
• Sync Path: A background Service Worker detects connectivity. When Online = True, it pushes a "Journal of Actions" to the Central Server.

2.2 Conflict Resolution: The "Append-Only" Ledger (ADR-002)

To prevent data corruption when multiple devices sync later, we do not store "Total Stock." We store Transactions.

• Wrong Way: Overwriting Stock = 490 (Causes race conditions).
• YAKAP-Link Way: Recording Action: DISPENSE, Qty: -10, Time: 10:00 AM.

The server replays these logs to calculate the final state, ensuring mathematical consistency even if devices sync days apart.

• Frontend: Astro (Shell) + React (Interactive UI).
• Local Database: RxDB (IndexedDB wrapper for robust local storage & replication).
• Styling: TailwindCSS.
• Backend: Node.js / Python + PostgreSQL (NeonDB).

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3. "The Balancer": Intelligent Redistribution Engine

This module transforms the system from a simple logger into a Waste Prevention Engine. It runs nightly on the Central Server to optimize stock levels across the entire province/region.

3.1 The Logic: Days of Inventory (DOI)

We normalize stock levels based on consumption velocity, not just quantity.

$$ DOI=Average Daily Consumption (ADC)Current Stock Level​ $$

• ADC: Calculated using a 30-day rolling average to account for recent outbreaks (e.g., Dengue season).

3.2 The "Expiry Pressure" Variable (

$$ Texp​ $$ )

We implement a FENO (First-Expired-Network-Out) strategy. If stock is expiring, the "Overstock Threshold" tightens dynamically to force a transfer.

The Formula:

$$ Thresholddynamic​=Thresholdbase​×(12Months to Expiry​) $$

• Scenario: If stock expires in 3 months, the system lowers the "Hoarding Limit" drastically. If an RHU holds more than 22 days of stock, it is flagged as "Critical Surplus" and routed to a high-volume hospital.

3.3 Offline Integrity: Protocol-20k-Guard (ADR-004)

To prevent "Double-Dipping" of benefits (₱20k ABL) while offline, we verify eligibility locally:

1. Home Court Rule: Visitor patients (from other municipalities) are blocked from offline dispensing. They require an online verification.
2. Staleness Cap: If the device hasn't synced in >72 hours, dispensing is capped at a 7-day emergency supply to limit liability.

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4. Operational Workflows

4.1 Field Usage (The Nurse's View)

1. Login: Offline auth using cached credentials.
2. Dispense: Nurse scans QR / selects med. Stock updates instantly (-1).
3. Sync: When the nurse travels to the town proper (or signal returns), the app auto-syncs in the background. Green checkmark appears.

4.2 The "Robin Hood" Alert (The Officer's View)

Instead of boring spreadsheets, the Municipal Health Officer receives actionable "Missions":

⚠️ Waste Prevention Alert

You have 500 vials of Insulin expiring in 4 months. Based on current usage, 350 vials are at risk of expiration.

Action: A transfer order has been generated for Provincial Hospital (20km away). [Click to Approve Transfer]

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5. Value Proposition

Feature	Old System (Cloud-Based)	YAKAP-Link (Local-First)
Connectivity	Requires 24/7 Internet	Works 100% Offline
Speed	Slow (Server Latency)	Instant (Zero Latency)
Inventory	Static Numbers	Predictive Redistribution
Compliance	"System Down" Excuses	Audit-Ready Logs
Waste	High (Expired in Warehouse)	Near Zero (FENO Logic)

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6. Roadmap & Implementation

1. Phase 1 (Core): Build the Offline-First Dispensing App (PWA).
2. Phase 2 (Sync): Deploy the PostgreSQL backend and Sync Service.
3. Phase 3 (Brain): Activate "The Balancer" algorithm for automated redistribution recommendations.

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Authored by: Alfie Tech Stack Reference: FieldLogic Core