diff --git a/src/lib/quota/storeFactory.ts b/src/lib/quota/storeFactory.ts
new file mode 100644
index 0000000000..a80e111e19
--- /dev/null
+++ b/src/lib/quota/storeFactory.ts
@@ -0,0 +1,124 @@
+/**
+ * storeFactory.ts — Lazy singleton factory for QuotaStore.
+ *
+ * Driver selection precedence (highest to lowest):
+ *   1. DB setting `quotaStore.driver` (read via getSettings())
+ *   2. Env `QUOTA_STORE_DRIVER`
+ *   3. Default: "sqlite"
+ *
+ * Redis URL precedence:
+ *   1. DB setting `quotaStore.redisUrl`
+ *   2. Env `QUOTA_STORE_REDIS_URL`
+ *
+ * If driver=redis but URL is absent/invalid → fallback to sqlite + pino.warn.
+ * Never throws — always returns a valid QuotaStore.
+ *
+ * Part of: Group B — Quota Sharing Engine (plan 22, frente F6).
+ */
+
+import { createLogger } from "@/shared/utils/logger";
+import type { QuotaStore } from "./types";
+
+const log = createLogger("quota:factory");
+
+// ---------------------------------------------------------------------------
+// Singleton state
+// ---------------------------------------------------------------------------
+
+let _store: QuotaStore | null = null;
+
+/** Reset the singleton (test-only). */
+export function resetQuotaStoreSingleton(): void {
+  _store = null;
+}
+
+// ---------------------------------------------------------------------------
+// Settings reader (async, best-effort)
+// ---------------------------------------------------------------------------
+
+interface QuotaStoreSettings {
+  driver?: string;
+  redisUrl?: string;
+}
+
+async function readDbSettings(): Promise<QuotaStoreSettings> {
+  try {
+    // Lazy import to avoid circular deps and to keep the module loadable
+    // in environments without a DB (e.g. partial test setups).
+    const { getSettings } = await import("@/lib/db/settings");
+    const settings = await getSettings();
+    const raw = settings["quotaStore"];
+    if (raw && typeof raw === "object" && !Array.isArray(raw)) {
+      const obj = raw as Record<string, unknown>;
+      return {
+        driver: typeof obj.driver === "string" ? obj.driver : undefined,
+        redisUrl: typeof obj.redisUrl === "string" ? obj.redisUrl : undefined,
+      };
+    }
+  } catch {
+    // DB not available — fall through to env
+  }
+  return {};
+}
+
+// ---------------------------------------------------------------------------
+// Public factory
+// ---------------------------------------------------------------------------
+
+/**
+ * Return the singleton QuotaStore, initialising it on first call.
+ *
+ * This function is async only because reading DB settings is async.
+ * After the first call it returns synchronously from the cached singleton.
+ */
+export async function getQuotaStore(): Promise<QuotaStore> {
+  if (_store) return _store;
+
+  // Read settings
+  const dbSettings = await readDbSettings();
+
+  const driver =
+    dbSettings.driver ?? process.env.QUOTA_STORE_DRIVER ?? "sqlite";
+
+  const redisUrl =
+    dbSettings.redisUrl ?? process.env.QUOTA_STORE_REDIS_URL ?? "";
+
+  if (driver === "redis") {
+    if (!redisUrl) {
+      log.warn("QUOTA_STORE_DRIVER=redis but no Redis URL configured — falling back to sqlite");
+    } else {
+      try {
+        const { getRedisQuotaStore } = await import("./redisQuotaStore");
+        // Validate ioredis is available by attempting a mock import
+        // The actual connection is lazy; we just need the class to instantiate.
+        const store = getRedisQuotaStore(redisUrl);
+        _store = store;
+        log.info({ redisUrl: redisUrl.replace(/:[^:@]*@/, ":***@") }, "QuotaStore: using Redis driver");
+        return _store;
+      } catch (err) {
+        log.warn(
+          { err: (err as Error)?.message },
+          "Redis QuotaStore unavailable — falling back to sqlite"
+        );
+        // Fall through to sqlite
+      }
+    }
+  }
+
+  // Default: SQLite
+  const { getSqliteQuotaStore } = await import("./sqliteQuotaStore");
+  _store = getSqliteQuotaStore();
+  log.info("QuotaStore: using SQLite driver");
+  return _store;
+}
+
+/**
+ * Synchronous version for callers that know the store has been initialised.
+ * Throws if called before getQuotaStore() has resolved.
+ */
+export function getQuotaStoreSync(): QuotaStore {
+  if (!_store) {
+    throw new Error("QuotaStore has not been initialised yet. Call getQuotaStore() first.");
+  }
+  return _store;
+}