don't overflow the server

backend/src/routes/tiles.rs

@@ -69,8 +69,11 @@ pub async fn get_tile(
     // Fetch from Martin
     let (data, etag): (Bytes, Option<String>) = martin.get_tile(&layer, z, x, y).await?;
 
-    // Store in cache (fire-and-forget)
+    // Store in cache — spawn so the client doesn't wait for the Redis write.
-    cache.set_tile(&cache_key, &data).await;
+    let cache2 = cache.clone();
+    let key2 = cache_key.clone();
+    let data2 = data.clone();
+    tokio::spawn(async move { cache2.set_tile(&key2, &data2).await });
 
     let mut resp = HttpResponse::Ok();
     resp.content_type("application/x-protobuf")

mobile/lib/features/map/presentation/screens/map_screen.dart

@@ -75,6 +75,7 @@ class _MapScreenState extends ConsumerState<MapScreen> {
                 data: (style) => VectorTileLayer(
                   tileProviders: style.providers,
                   theme: style.theme,
+                  concurrency: 4,
                 ),
                 loading: () => const SizedBox.shrink(),
                 error: (e, _) => const SizedBox.shrink(),