# Implementation Plan: High-Integrity Cache & Database Synchronization

## Phase 1: Infrastructure & Core Utilities [checkpoint: b314c26] [MCP: FileSystem] [Skills: Repository-Pattern-Enforcer]
- [x] Task 1.1: [Scout] Analyze `lib/db/schema.ts` for existing `updated_at` or versioning fields. [Skills: codebase_investigator]
- [x] Task 1.2: [Write Failing Tests] Define the schema for the `sync_retry_queue` table and its associated Zod validation. [Skills: test-driven-development]
- [x] Task 1.3: [Implement] Create the `sync_retry_queue` migration and update the database schema. [Skills: managing-schemas]
- [x] Task 1.4: [Implement] Create Tiered Security utilities in `lib/security-tiers.ts` for encryption (AES-256) and hashing. [Skills: securing-applications]
- [ ] Phase Completion Verification: [Meta-Task: Manual Verification]

## Phase 2: Synchronization Layer implementation [checkpoint: 92df19b] [MCP: FileSystem] [Skills: Applying-DRY-Principles]
- [x] Task 2.1: [Scout] Review `lib/db/repositories/base.repository.ts` for current generic query/write methods. [Skills: codebase_investigator]
- [x] Task 2.2: [Write Failing Tests] Implement unit tests for `BaseRepository` to ensure it handles cache lookups and DB fallbacks correctly. [Skills: test-driven-development]
- [x] Task 2.3: [Implement] Update `BaseRepository` with `cacheFirstFind` (Read-Aside) and `atomicSyncWrite` (Write-Through) methods.
- [x] Task 2.4: [Implement] Implement the `SyncService` to handle `sync_retry_queue` insertions upon Redis failure. [Skills: architecting-automation]
- [ ] Phase Completion Verification: [Meta-Task: Manual Verification]

## Phase 3: Integration & Security Tiers [checkpoint: 56ca2ce] [MCP: FileSystem, Shell] [Skills: Fullstack-Development]
- [x] Task 3.1: [Scout] Identify repositories that handle sensitive data (PII vs. Catalog). [Skills: codebase_investigator]
- [x] Task 3.2: [Write Failing Tests] Add tests for `CustomerRepository` (Sensitive) and `CatalogRepository` (Non-Sensitive) verifying tiered cache behavior. [Skills: test-driven-development]
- [x] Task 3.3: [Implement] Apply tiered synchronization to `CustomerRepository` (Encrypted) and `CatalogRepository` (Plaintext). [Skills: securing-applications]
- [ ] Phase Completion Verification: [Meta-Task: Manual Verification]

## Phase 4: Resiliency & Background Recovery [checkpoint: d87769e] [MCP: Shell] [Skills: Systematic-Debugging]
- [x] Task 4.1: [Scout] Review `lib/actions.ts` and `lib/utils.ts` for existing retry patterns. [Skills: codebase_investigator]
- [x] Task 4.2: [Write Failing Tests] Simulate Redis downtime and verify `sync_retry_queue` population and successful replay. [Skills: test-driven-development]
- [x] Task 4.3: [Implement] Create a background synchronization worker in `lib/sync-worker.ts` that processes the `sync_retry_queue`. [Skills: architecting-automation]
- [ ] Phase Completion Verification: [Meta-Task: Manual Verification]

## Phase 5: Integrity & Gap Closure [checkpoint: 27c365a] [MCP: Shell] [Skills: Systematic-Debugging]
- [x] Task 5.1: [Scout] Investigate potential race conditions during concurrent updates. [Skills: codebase_investigator]
- [x] Task 5.2: [Write Failing Tests] Create high-concurrency tests for `atomicSyncWrite` using multiple parallel workers. [Skills: test-driven-development]
- [x] Task 5.3: [Implement] Implement Redis Lua scripts or versioned update logic to ensure atomic cache updates under high load. [Skills: applying-dry-principles]
- [x] Task 5.4: [Implement] Implement a "Cold Start" cache warming strategy for when Redis is cleared. [Skills: architecting-automation]
- [x] Task 5.5: [Implement] Ensure that DB rollbacks automatically invalidate the corresponding Cache entries. [Skills: fullstack-development]
- [x] Task 5.6: [Quality Gate] Perform a full **Strictness Audit** (Linting, Types) and verify 100% test coverage with real Redis. [Skills: verification-before-completion]
- [x] Phase Completion Verification: [Meta-Task: Manual Verification]

## Phase: Review Fixes
- [x] Task: Apply review suggestions f577ff3