diff --git a/lightrag/storage.py b/lightrag/storage.py
index 007d6534..4c043893 100644
--- a/lightrag/storage.py
+++ b/lightrag/storage.py
@@ -107,10 +107,16 @@ async def upsert(self, data: dict[str, dict]):
             embeddings = await f
             embeddings_list.append(embeddings)
         embeddings = np.concatenate(embeddings_list)
-        for i, d in enumerate(list_data):
-            d["__vector__"] = embeddings[i]
-        results = self._client.upsert(datas=list_data)
-        return results
+        if len(embeddings) == len(list_data):
+            for i, d in enumerate(list_data):
+                d["__vector__"] = embeddings[i]
+            results = self._client.upsert(datas=list_data)
+            return results
+        else:
+            # sometimes the embedding is not returned correctly. just log it.
+            logger.error(
+                f"embedding is not 1-1 with data, {len(embeddings)} != {len(list_data)}"
+            )
 
     async def query(self, query: str, top_k=5):
         embedding = await self.embedding_func([query])
diff --git a/lightrag/utils.py b/lightrag/utils.py
index 0220af06..bdb47592 100644
--- a/lightrag/utils.py
+++ b/lightrag/utils.py
@@ -17,6 +17,17 @@
 
 from lightrag.prompt import PROMPTS
 
+
+class UnlimitedSemaphore:
+    """A context manager that allows unlimited access."""
+
+    async def __aenter__(self):
+        pass
+
+    async def __aexit__(self, exc_type, exc, tb):
+        pass
+
+
 ENCODER = None
 
 logger = logging.getLogger("lightrag")
@@ -42,9 +53,17 @@ class EmbeddingFunc:
     embedding_dim: int
     max_token_size: int
     func: callable
+    concurrent_limit: int = 16
+
+    def __post_init__(self):
+        if self.concurrent_limit != 0:
+            self._semaphore = asyncio.Semaphore(self.concurrent_limit)
+        else:
+            self._semaphore = UnlimitedSemaphore()
 
     async def __call__(self, *args, **kwargs) -> np.ndarray:
-        return await self.func(*args, **kwargs)
+        async with self._semaphore:
+            return await self.func(*args, **kwargs)
 
 
 def locate_json_string_body_from_string(content: str) -> Union[str, None]: