diff --git a/lib_vector_search/include/bucket_finder.h b/lib_vector_search/include/bucket_finder.h
index d8eae45..15b7dbe 100644
--- a/lib_vector_search/include/bucket_finder.h
+++ b/lib_vector_search/include/bucket_finder.h
@@ -7,7 +7,7 @@
 
 class Bucket {
 private:
-  std::map<const char, WordRefList> groups_;
+  std::map<char, WordRefList> directory_;
 
 public:
   void insert(const WordList &word_list, size_t first_index, size_t last_index);
diff --git a/lib_vector_search/src/bucket_finder.cpp b/lib_vector_search/src/bucket_finder.cpp
index 2738b0b..8fd7500 100644
--- a/lib_vector_search/src/bucket_finder.cpp
+++ b/lib_vector_search/src/bucket_finder.cpp
@@ -6,20 +6,20 @@
 
 void Bucket::insert(const WordList &word_list, size_t first_index,
                     size_t last_index) {
-  for (size_t index = first_index; index < last_index; ++index) {
+  for (auto index = first_index; index < last_index; ++index) {
     const auto &current_word = word_list[index];
-    groups_[current_word.front()].push_back(&current_word);
+    directory_[current_word.front()].push_back(&current_word);
   }
 }
 
 WordRefList Bucket::find_prefix(std::string_view search_term) const {
-  auto group_it = groups_.find(search_term.front());
-  if (group_it == groups_.cend()) {
+  auto directory_it = directory_.find(search_term.front());
+  if (directory_it == directory_.cend()) {
     return {};
   }
 
   WordRefList result;
-  for (const auto *word : group_it->second) {
+  for (const auto *word : directory_it->second) {
     if (word->starts_with(search_term)) {
       result.push_back(word);
     }