OBJ then local

lib/storage.ts

@@ -16,6 +16,7 @@ import {
   DeleteObjectCommand,
   GetObjectCommand,
   ListObjectsV2Command,
+  HeadObjectCommand,
 } from "@aws-sdk/client-s3";
 import { getSignedUrl } from "@aws-sdk/s3-request-presigner";
 import fs from "fs";
@@ -278,6 +279,30 @@ export async function uploadToHetzner(
   return { key };
 }
 
+/**
+ * In-process cache for Hetzner key existence checks.
+ * Positive hits (key exists) are cached indefinitely for the process lifetime
+ * since uploaded files are immutable UUID-named objects that never disappear.
+ * Negative hits are not cached so newly-migrated files are picked up immediately.
+ */
+const hetznerExistsCache = new Map<string, true>();
+
+/**
+ * Returns true if the given key exists in the Hetzner bucket.
+ * Results are cached in process memory after the first check.
+ */
+export async function hetznerKeyExists(key: string): Promise<boolean> {
+  if (hetznerExistsCache.has(key)) return true;
+  try {
+    const { client, bucket } = await buildHetznerClient();
+    await client.send(new HeadObjectCommand({ Bucket: bucket, Key: key }));
+    hetznerExistsCache.set(key, true);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
 /**
  * List all object keys currently stored in the Hetzner bucket.
  * Paginates automatically. Used by the migration tool.