diff --git a/prompting/rewards/web_retrieval.py b/prompting/rewards/web_retrieval.py
index 6de4242fc..9fbfaff91 100644
--- a/prompting/rewards/web_retrieval.py
+++ b/prompting/rewards/web_retrieval.py
@@ -3,6 +3,7 @@
 import json
 import os
 from collections import defaultdict
+from functools import lru_cache
 from urllib.parse import urlparse
 
 import numpy as np
@@ -83,6 +84,7 @@ class WebsiteResult(BaseModel):
 
 
 class WebRetrievalRewardModel(RelevanceRewardModel):
+    @lru_cache(maxsize=1000)
     def _cosine_similarity(self, content1: str, content2: str) -> float:
         """Calculate the cosine similarity between sentence embeddings of the reference and completions."""
         reference_emb_flatten = self.embedding_model.encode(content1, to_numpy=True).flatten()