diff --git a/cpp/include/cudf/io/types.hpp b/cpp/include/cudf/io/types.hpp
index 76899092b30..9d6a83e8730 100644
--- a/cpp/include/cudf/io/types.hpp
+++ b/cpp/include/cudf/io/types.hpp
@@ -126,7 +126,7 @@ struct table_metadata {
     schema_info;  //!< Detailed name information for the entire output hierarchy
   std::map<std::string, std::string> user_data;  //!< Format-dependent metadata of the first input
                                                  //!< file as key-values pairs (deprecated)
-  std::vector<std::map<std::string, std::string>>
+  std::vector<std::unordered_map<std::string, std::string>>
     per_file_user_data;  //!< Per file format-dependent metadata as key-values pairs
 };
 
diff --git a/cpp/src/io/avro/reader_impl.cu b/cpp/src/io/avro/reader_impl.cu
index fbc32217e59..f39fba0d33b 100644
--- a/cpp/src/io/avro/reader_impl.cu
+++ b/cpp/src/io/avro/reader_impl.cu
@@ -575,7 +575,7 @@ table_with_metadata read_avro(std::unique_ptr<cudf::io::datasource>&& source,
   }
   // Return user metadata
   metadata_out.user_data          = meta.user_data;
-  metadata_out.per_file_user_data = {meta.user_data};
+  metadata_out.per_file_user_data = {{meta.user_data.begin(), meta.user_data.end()}};
 
   return {std::make_unique<table>(std::move(out_columns)), std::move(metadata_out)};
 }
diff --git a/cpp/src/io/orc/reader_impl.cu b/cpp/src/io/orc/reader_impl.cu
index 7b25204db1c..f64ba6f0566 100644
--- a/cpp/src/io/orc/reader_impl.cu
+++ b/cpp/src/io/orc/reader_impl.cu
@@ -1266,13 +1266,17 @@ table_with_metadata reader::impl::read(size_type skip_rows,
                  _metadata.per_file_metadata.cend(),
                  std::back_inserter(out_metadata.per_file_user_data),
                  [](auto& meta) {
-                   std::map<std::string, std::string> kv_map;
-                   for (auto& kv : meta.ff.metadata) {
-                     kv_map[kv.name] = kv.value;
-                   }
+                   std::unordered_map<std::string, std::string> kv_map;
+                   std::transform(meta.ff.metadata.cbegin(),
+                                  meta.ff.metadata.cend(),
+                                  std::inserter(kv_map, kv_map.end()),
+                                  [](auto const& kv) {
+                                    return std::pair{kv.name, kv.value};
+                                  });
                    return kv_map;
                  });
-  out_metadata.user_data = out_metadata.per_file_user_data[0];
+  out_metadata.user_data = {out_metadata.per_file_user_data[0].begin(),
+                            out_metadata.per_file_user_data[0].end()};
 
   return {std::make_unique<table>(std::move(out_columns)), std::move(out_metadata)};
 }
diff --git a/cpp/src/io/parquet/reader_impl.cu b/cpp/src/io/parquet/reader_impl.cu
index 06e87b8e0c4..c3537833908 100644
--- a/cpp/src/io/parquet/reader_impl.cu
+++ b/cpp/src/io/parquet/reader_impl.cu
@@ -318,7 +318,7 @@ struct metadata : public FileMetaData {
 
 class aggregate_reader_metadata {
   std::vector<metadata> per_file_metadata;
-  std::vector<std::map<std::string, std::string>> keyval_maps;
+  std::vector<std::unordered_map<std::string, std::string>> keyval_maps;
   size_type num_rows;
   size_type num_row_groups;
   /**
@@ -339,12 +339,12 @@ class aggregate_reader_metadata {
    */
   [[nodiscard]] auto collect_keyval_metadata()
   {
-    std::vector<std::map<std::string, std::string>> kv_maps;
+    std::vector<std::unordered_map<std::string, std::string>> kv_maps;
     std::transform(per_file_metadata.cbegin(),
                    per_file_metadata.cend(),
                    std::back_inserter(kv_maps),
                    [](auto const& pfm) {
-                     std::map<std::string, std::string> kv_map;
+                     std::unordered_map<std::string, std::string> kv_map;
                      std::transform(pfm.key_value_metadata.cbegin(),
                                     pfm.key_value_metadata.cend(),
                                     std::inserter(kv_map, kv_map.end()),
@@ -1770,7 +1770,8 @@ table_with_metadata reader::impl::read(size_type skip_rows,
 
   // Return user metadata
   out_metadata.per_file_user_data = _metadata->get_key_value_metadata();
-  out_metadata.user_data          = out_metadata.per_file_user_data[0];
+  out_metadata.user_data          = {out_metadata.per_file_user_data[0].begin(),
+                            out_metadata.per_file_user_data[0].end()};
 
   return {std::make_unique<table>(std::move(out_columns)), std::move(out_metadata)};
 }