diff --git a/application/src/main/java/run/halo/app/core/attachment/extension/LocalThumbnail.java b/application/src/main/java/run/halo/app/core/attachment/extension/LocalThumbnail.java
index 97ee3974b1..7cf66c1b18 100644
--- a/application/src/main/java/run/halo/app/core/attachment/extension/LocalThumbnail.java
+++ b/application/src/main/java/run/halo/app/core/attachment/extension/LocalThumbnail.java
@@ -19,6 +19,7 @@
 @GVK(group = "storage.halo.run", version = "v1alpha1", kind = "LocalThumbnail",
     plural = "localthumbnails", singular = "localthumbnail")
 public class LocalThumbnail extends AbstractExtension {
+    public static final String UNIQUE_IMAGE_AND_SIZE_INDEX = "uniqueImageAndSize";
     public static final String REQUEST_TO_GENERATE_ANNO = "storage.halo.run/request-to-generate";
 
     @Schema(requiredMode = REQUIRED)
@@ -80,4 +81,13 @@ public static class Status {
     public enum Phase {
         PENDING, SUCCEEDED, FAILED
     }
+
+    public static String uniqueImageAndSize(LocalThumbnail localThumbnail) {
+        return uniqueImageAndSize(localThumbnail.getSpec().getImageSignature(),
+            localThumbnail.getSpec().getSize());
+    }
+
+    public static String uniqueImageAndSize(String imageSignature, ThumbnailSize size) {
+        return imageSignature + "-" + size.name();
+    }
 }
diff --git a/application/src/main/java/run/halo/app/core/attachment/impl/LocalThumbnailServiceImpl.java b/application/src/main/java/run/halo/app/core/attachment/impl/LocalThumbnailServiceImpl.java
index 5b25d4b012..3ed0ddf2bc 100644
--- a/application/src/main/java/run/halo/app/core/attachment/impl/LocalThumbnailServiceImpl.java
+++ b/application/src/main/java/run/halo/app/core/attachment/impl/LocalThumbnailServiceImpl.java
@@ -64,8 +64,8 @@ private static Path buildThumbnailStorePath(Path rootPath, String fileName, Stri
             .resolve(fileName);
     }
 
-    static String geImageFileName(URL imageUrl) {
-        var fileName = substringAfterLast(imageUrl.getPath(), "/");
+    static String geImageFileName(URI imageUri) {
+        var fileName = substringAfterLast(imageUri.getPath(), "/");
         fileName = defaultIfBlank(fileName, randomAlphanumeric(10));
         return ThumbnailGenerator.sanitizeFileName(fileName);
     }
@@ -113,11 +113,12 @@ private Mono<LocalThumbnail> fetchThumbnail(URI thumbnailUri) {
 
     private Mono<LocalThumbnail> fetchByImageHashAndSize(String imageSignature,
         ThumbnailSize size) {
+        var indexValue = LocalThumbnail.uniqueImageAndSize(imageSignature, size);
         return client.listBy(LocalThumbnail.class, ListOptions.builder()
-                .fieldQuery(equal("spec.imageSignature", imageSignature))
-                .build(), PageRequestImpl.ofSize(ThumbnailSize.values().length))
+                .fieldQuery(equal(LocalThumbnail.UNIQUE_IMAGE_AND_SIZE_INDEX, indexValue))
+                .build(), PageRequestImpl.ofSize(ThumbnailSize.values().length)
+            )
             .flatMapMany(result -> Flux.fromIterable(result.getItems()))
-            .filter(thumbnail -> thumbnail.getSpec().getSize().equals(size))
             .next();
     }
 
@@ -158,9 +159,15 @@ private Mono<Void> updateWithRetry(LocalThumbnail localThumbnail, Consumer<Local
     public Mono<LocalThumbnail> create(URL imageUrl, ThumbnailSize size) {
         Assert.notNull(imageUrl, "Image URL must not be null.");
         Assert.notNull(size, "Thumbnail size must not be null.");
-        var year = getYear();
-        var originalFileName = geImageFileName(imageUrl);
         var imageUri = URI.create(imageUrl.toString());
+        var imageHash = signatureForImageUri(imageUri);
+        return fetchByImageHashAndSize(imageHash, size)
+            .switchIfEmpty(Mono.defer(() -> doCreate(imageUri, size)));
+    }
+
+    private Mono<LocalThumbnail> doCreate(URI imageUri, ThumbnailSize size) {
+        var year = getYear();
+        var originalFileName = geImageFileName(imageUri);
         return generateUniqueThumbFileName(originalFileName, year, size)
             .flatMap(thumbFileName -> {
                 var filePath =
diff --git a/application/src/main/java/run/halo/app/infra/SchemeInitializer.java b/application/src/main/java/run/halo/app/infra/SchemeInitializer.java
index 49ab3d0a64..c8dd622f05 100644
--- a/application/src/main/java/run/halo/app/infra/SchemeInitializer.java
+++ b/application/src/main/java/run/halo/app/infra/SchemeInitializer.java
@@ -612,6 +612,14 @@ public void onApplicationEvent(@NonNull ApplicationContextInitializedEvent event
             );
         });
         schemeManager.register(LocalThumbnail.class, indexSpec -> {
+            // make sure image and size are unique
+            indexSpec.add(new IndexSpec()
+                .setUnique(true)
+                .setName(LocalThumbnail.UNIQUE_IMAGE_AND_SIZE_INDEX)
+                .setIndexFunc(simpleAttribute(LocalThumbnail.class,
+                    LocalThumbnail::uniqueImageAndSize)
+                )
+            );
             indexSpec.add(new IndexSpec()
                 .setName("spec.imageSignature")
                 .setIndexFunc(simpleAttribute(LocalThumbnail.class,
diff --git a/application/src/test/java/run/halo/app/core/attachment/impl/LocalThumbnailServiceImplTest.java b/application/src/test/java/run/halo/app/core/attachment/impl/LocalThumbnailServiceImplTest.java
index 54d3d2c432..6970e89ab1 100644
--- a/application/src/test/java/run/halo/app/core/attachment/impl/LocalThumbnailServiceImplTest.java
+++ b/application/src/test/java/run/halo/app/core/attachment/impl/LocalThumbnailServiceImplTest.java
@@ -12,6 +12,7 @@
 import java.net.MalformedURLException;
 import java.net.URI;
 import java.net.URL;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -20,6 +21,7 @@
 import org.mockito.InjectMocks;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.web.util.UriUtils;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 import run.halo.app.core.attachment.AttachmentRootGetter;
@@ -61,14 +63,14 @@ void endpointForTest() {
     @Test
     void geImageFileNameTest() throws MalformedURLException {
         var fileName =
-            LocalThumbnailServiceImpl.geImageFileName(new URL("https://halo.run/example.jpg"));
+            LocalThumbnailServiceImpl.geImageFileName(URI.create("https://halo.run/example.jpg"));
         assertThat(fileName).isEqualTo("example.jpg");
 
-        fileName = LocalThumbnailServiceImpl.geImageFileName(new URL("https://halo.run/"));
+        fileName = LocalThumbnailServiceImpl.geImageFileName(URI.create("https://halo.run/"));
         assertThat(fileName).isNotBlank();
 
-        fileName = LocalThumbnailServiceImpl.geImageFileName(
-            new URL("https://halo.run/.1fasfg(*&^%$.jpg"));
+        var encoded = UriUtils.encode("https://halo.run/.1fasfg(*&^%$.jpg", StandardCharsets.UTF_8);
+        fileName = LocalThumbnailServiceImpl.geImageFileName(URI.create(encoded));
         assertThat(fileName).isNotBlank();
     }