diff --git a/src/actions/transformations/html_entity_decode.cc b/src/actions/transformations/html_entity_decode.cc
index e22c5419..38351679 100644
--- a/src/actions/transformations/html_entity_decode.cc
+++ b/src/actions/transformations/html_entity_decode.cc
@@ -47,7 +47,7 @@ std::string HtmlEntityDecode::evaluate(std::string value,
     ret.assign(tmp);
     free(tmp);
 
-    HtmlEntityDecodeInstantCache::getInstance().emplace(value, ret);
+    HtmlEntityDecodeInstantCache::getInstance().cache(value, ret);
 
     return ret;
 }
diff --git a/src/actions/transformations/html_entity_decode.h b/src/actions/transformations/html_entity_decode.h
index 131ebef5..1dcdda32 100644
--- a/src/actions/transformations/html_entity_decode.h
+++ b/src/actions/transformations/html_entity_decode.h
@@ -37,6 +37,12 @@ class HtmlEntityDecodeInstantCache : public std::unordered_map<std::string, std:
         return instance;
     }
 
+    void cache(const std::string& value, const std::string& out) {
+        emplace(value, out);
+        if (size() > 100) {
+            erase(begin());
+        }
+    }
  private:
     HtmlEntityDecodeInstantCache() {};
 };
diff --git a/src/actions/transformations/lower_case.cc b/src/actions/transformations/lower_case.cc
index a2c98edb..6f523670 100644
--- a/src/actions/transformations/lower_case.cc
+++ b/src/actions/transformations/lower_case.cc
@@ -45,7 +45,7 @@ std::string LowerCase::evaluate(std::string value,
         value[i] = std::tolower(value[i], loc);
     }
 
-    LowerCaseInstantCache::getInstance().emplace(orig_value, value);
+    LowerCaseInstantCache::getInstance().cache(orig_value, value);
 
     return value;
 }
diff --git a/src/actions/transformations/lower_case.h b/src/actions/transformations/lower_case.h
index 80e8addf..b26fb0d9 100644
--- a/src/actions/transformations/lower_case.h
+++ b/src/actions/transformations/lower_case.h
@@ -36,6 +36,12 @@ class LowerCaseInstantCache : public std::unordered_map<std::string, std::string
         return instance;
     }
 
+    void cache(const std::string& value, const std::string& out) {
+        emplace(value, out);
+        if (size() > 100) {
+            erase(begin());
+        }
+    }
  private:
     LowerCaseInstantCache() {};
 };
diff --git a/src/actions/transformations/url_decode.cc b/src/actions/transformations/url_decode.cc
index 176f734b..e901c597 100644
--- a/src/actions/transformations/url_decode.cc
+++ b/src/actions/transformations/url_decode.cc
@@ -116,7 +116,7 @@ std::string UrlDecode::evaluate(std::string value,
 
     free(val);
 
-    UrlDecodeInstantCache::getInstance().emplace(value, out);
+    UrlDecodeInstantCache::getInstance().cache(value, out);
 
     return out;
 }
diff --git a/src/actions/transformations/url_decode.h b/src/actions/transformations/url_decode.h
index a2f2c587..acadbbda 100644
--- a/src/actions/transformations/url_decode.h
+++ b/src/actions/transformations/url_decode.h
@@ -36,6 +36,12 @@ class UrlDecodeInstantCache : public std::unordered_map<std::string, std::string
         return instance;
     }
 
+    void cache(const std::string& value, const std::string& out) {
+        emplace(value, out);
+        if (size() > 100) {
+            erase(begin());
+        }
+    }
  private:
     UrlDecodeInstantCache() {};
 };