more stuff

cmd/cart/pool-server.go

@@ -201,6 +201,19 @@ type itemGroup struct {
 // become authoritative for what the projection carries; HTTP stays for
 // dimensions (parent width/height for child pricing), seller/orgPrice and the
 // dynamic ExtraJson product data. Skipped cleanly when idx is nil.
+//
+// Cache-only fast path: a parent with NO children AND a cache hit that
+// satisfies HasRequiredFields skips PRODUCT_BASE_URL entirely — BuildAddItem-
+// FromCache constructs the line directly from the Projection. This eliminates
+// the per-add HTTP round-trip under steady-state bus-fed conditions for the
+// common top-level add case. The HTTP path continues to handle:
+//   - cache miss (cold-grace; a SKU not yet bus-fed)
+//   - HasRequiredFields==false (partial bus delivery, e.g. TaxClass missing
+//     because the producer didn't classify)
+//   - parents WITH children (configurator behavior preservation — child
+//     price = child per-m² rate × parent area, and parent area comes from
+//     HTTP-fetched width/height that the Projection doesn't carry yet; a
+//     future schema extension can unblock a child cache-only path).
 func buildItemGroups(ctx context.Context, items []Item, country string, idx *catalogProjectionCache) []itemGroup {
 	groups := make([]itemGroup, len(items))
 	wg := sync.WaitGroup{}
@@ -210,14 +223,27 @@ func buildItemGroups(ctx context.Context, items []Item, country string, idx *cat
 				log.Printf("error adding item %s: bus-deleted (skipping)", itm.Sku)
 				return
 			}
-			parentMsg, parentProduct, err := BuildItemMessage(ctx, itm.Sku, itm.Quantity, country, itm.StoreId, nil)
-			if err != nil {
-				log.Printf("error adding item %s: %v", itm.Sku, err)
-				return
+
+			// Cache-only fast path: see package doc above for the eligibility
+			// contract.
+			var parentMsg *messages.AddItem
+			var parentProduct *ProductItem
+			if len(itm.Children) == 0 && idx != nil {
+				if p, ok := idx.Get(itm.Sku); ok && HasRequiredFields(p) {
+					parentMsg = BuildAddItemFromCache(itm.Sku, itm.Quantity, country, itm.StoreId, p)
+				}
 			}
-			if idx != nil {
-				if p, ok := idx.Get(itm.Sku); ok {
-					ApplyProjectionOverlay(parentMsg, p)
+			if parentMsg == nil {
+				var err error
+				parentMsg, parentProduct, err = BuildItemMessage(ctx, itm.Sku, itm.Quantity, country, itm.StoreId, nil)
+				if err != nil {
+					log.Printf("error adding item %s: %v", itm.Sku, err)
+					return
+				}
+				if idx != nil {
+					if p, ok := idx.Get(itm.Sku); ok {
+						ApplyProjectionOverlay(parentMsg, p)
+					}
 				}
 			}
 			parentMsg.CustomFields = itm.CustomFields