diff --git a/server/src/lib/image-resize.js b/server/src/lib/image-resize.js
new file mode 100644
index 0000000..e0b5d08
--- /dev/null
+++ b/server/src/lib/image-resize.js
@@ -0,0 +1,66 @@
+import crypto from 'node:crypto'
+import fs from 'node:fs'
+import path from 'node:path'
+
+const UPLOADS_DIR = path.join(process.cwd(), 'uploads')
+const CACHE_DIR = path.join(UPLOADS_DIR, '.cache')
+const VALID_WIDTHS = [320, 640, 1024, 1600]
+const SUPPORTED_FORMATS = new Set(['avif', 'webp'])
+
+/**
+ * Find the original file by UUID (without extension) in the uploads directory tree.
+ * Searches both /uploads/ and /uploads/reviews/.
+ * Returns full path or null.
+ */
+export async function findOriginalFile(uuid, subdir = '') {
+  const searchDirs = subdir ? [subdir] : ['', 'reviews']
+  for (const dir of searchDirs) {
+    for (const ext of ['.png', '.jpg', '.jpeg', '.webp']) {
+      const fullPath = path.join(UPLOADS_DIR, dir, `${uuid}${ext}`)
+      try {
+        await fs.promises.access(fullPath)
+        return fullPath
+      } catch {
+        // file not found with this extension, try next
+      }
+    }
+  }
+  return null
+}
+
+/**
+ * Get or generate a resized image. Returns { path: string, isNew: boolean }.
+ */
+export async function getOrCreateResized(uuid, width, format, subdir = '') {
+  const cacheSubdir = subdir ? subdir : ''
+  const cacheFileName = `${uuid}_w${width}.${format}`
+  const cachePath = path.join(CACHE_DIR, cacheSubdir, cacheFileName)
+
+  try {
+    await fs.promises.access(cachePath)
+    return { path: cachePath, isNew: false }
+  } catch {
+    // cache miss, need to generate
+  }
+
+  const originalPath = await findOriginalFile(uuid, subdir)
+  if (!originalPath) {
+    return null
+  }
+
+  await fs.promises.mkdir(path.dirname(cachePath), { recursive: true })
+
+  const sharp = (await import('sharp')).default
+  let pipeline = sharp(originalPath)
+
+  if (width) {
+    pipeline = pipeline.resize(width, null, { withoutEnlargement: true })
+  }
+
+  const options = format === 'avif' ? { quality: 75, effort: 4 } : { quality: 80 }
+  await pipeline[format](options).toFile(cachePath)
+
+  return { path: cachePath, isNew: true }
+}
+
+export { VALID_WIDTHS, SUPPORTED_FORMATS }