Merge pull request 'Backfill BFS derinligini 5->2'ye indir (sig pre-warm)' (#143) from dev into main

apps/api/src/jobs/prefetch-worker.service.ts

@@ -26,7 +26,18 @@ import {
 import { PrefetchCategoryJobData, PrefetchInitJobData } from "./prefetch.types";
 import { CATALOG_PREFETCH_QUEUE } from "./queues/catalog-prefetch.queue";
 
-const MAX_DEPTH = 5;
+/**
+ * How deep the background prefetch BFS drills the category tree.
+ *
+ * Kept SHALLOW (2) on purpose: pre-warming the top ~2 levels for every decoded
+ * vehicle is bounded work that finishes in days, kills empty catalog pages, and
+ * makes the first clicks instant. Deeper categories are fetched lazily on-view
+ * (getCategoryTree in CategoriesService) and cached permanently — so the long
+ * tail nobody opens never costs an upstream request. Exhaustive depth-5
+ * pre-warm produced an unbounded BFS fan-out (~460k jobs) that never drained
+ * and starved the useful shallow + reactive work. Env-tunable.
+ */
+const MAX_DEPTH = Number(process.env.PREFETCH_MAX_DEPTH) || 2;
 
 // ── Backfill scan (hourly cron) tuning ──
 /**