[Phase 1] Cache Tags & ProductSummary Denormalization Strategy

[syed-reza98]

Priority: P0 (Critical)

Phase: 1 - E-Commerce Core
Estimate: 2 days
Type: Story

Context

Implement targeted cache invalidation using Next.js cache tags plus a denormalized ProductSummary record to accelerate listing, cart, and merchandising queries.

Scope

• Denormalized table: ProductSummary (id, productId, storeId, title, price, active, inventoryAvailable, primaryImageUrl, updatedAt)
• Populate/refresh on product change, inventory change, price change
• Cache tags: product:{id}, store:{storeId}:products, inventory:{productId}
• Server components query ProductSummary for list views instead of full Product joins
• Invalidation function: revalidateProduct(productId) triggers relevant tags
• Background reconciliation job (daily) to ensure summary consistency

Acceptance Criteria

• Product create/update triggers ProductSummary mutation & cache tag revalidation
• Inventory change updates ProductSummary.inventoryAvailable within < 500ms
• Listing pages use ProductSummary only (no N+1 full product fetch)
• Stale reads after update < 5s (eventual consistency window)
• Reconciliation job logs discrepancies count (should trend to 0)

Data Model (Draft)

model ProductSummary {
  id                 String   @id @default(cuid())
  productId          String   @unique
  storeId            String
  title              String
  price              Int
  active             Boolean  @default(true)
  inventoryAvailable Int       @default(0)
  primaryImageUrl    String?
  updatedAt          DateTime  @updatedAt

  @@index([storeId])
}

Dependencies

• Relies on core Product & Inventory models
• Supports performance optimization for marketplace & multi-channel ([Phase 3] Epic: Multi-Channel Sales #35, [Phase 5] Epic: Advanced Reliability #37)

Metrics

• Product list query latency reduction > 30%
• Consistency discrepancy rate < 0.1%

Testing Checklist

• Product update reflected in ProductSummary & listing
• Inventory adjustment updates summary
• Cache tag revalidation removes stale page

Risk

Performance & correctness impact (score: 15). Enables scalable product browsing.

References

• docs/GITHUB_ISSUES_COMPARISON_ANALYSIS.md (cache tag gap section)