diff --git a/core-writer/include/MetadataBuffer.hpp b/core-writer/include/MetadataBuffer.hpp
index 9b72223..790d676 100644
--- a/core-writer/include/MetadataBuffer.hpp
+++ b/core-writer/include/MetadataBuffer.hpp
@@ -8,19 +8,28 @@
 
 class MetadataBuffer
 {
-	const uint64_t n_images;
-	const std::shared_ptr<std::unordered_map<std::string, HeaderDataType>> header_values_type;
+    typedef std::unordered_map<std::string, HeaderDataType> header_map;
+
+	const uint64_t n_slots_;
+	const header_map& header_values_type_;
 
 	protected:
 		std::unordered_map<std::string, std::shared_ptr<char>> metadata_buffer;
 		std::unordered_map<std::string, size_t> metadata_length_bytes;
 
 	public:
-		MetadataBuffer(uint64_t n_images, std::shared_ptr<std::unordered_map<std::string, HeaderDataType>> header_values_type);
-		void add_metadata_to_buffer(std::string name, uint64_t frame_index, const char* data);
+		MetadataBuffer(
+		        const uint64_t n_slots,
+		        const header_map& header_values_type);
+
+		void add_metadata_to_buffer(
+		        const std::string& name,
+		        const uint64_t frame_index,
+		        const char* data);
+
 		std::shared_ptr<char> get_metadata_values(std::string name);
-		std::shared_ptr<std::unordered_map<std::string, HeaderDataType>> get_header_values_type();
-		uint64_t get_n_images();
+		const header_map& get_header_values_type();
+		uint64_t get_n_slots();
 };
 
 #endif
diff --git a/core-writer/src/writer/MetadataBuffer.cpp b/core-writer/src/writer/MetadataBuffer.cpp
index 13777fa..c494116 100644
--- a/core-writer/src/writer/MetadataBuffer.cpp
+++ b/core-writer/src/writer/MetadataBuffer.cpp
@@ -6,46 +6,59 @@
 
 using namespace std;
 
-MetadataBuffer::MetadataBuffer(uint64_t n_images, shared_ptr<unordered_map<string, HeaderDataType>> header_values_type) :
-    n_images(n_images), header_values_type(header_values_type)
+MetadataBuffer::MetadataBuffer(
+        const uint64_t n_slots,
+        const header_map& header_values_type) :
+            n_slots_(n_slots),
+            header_values_type_(header_values_type)
 {
-    if (header_values_type) {
-        for (const auto& header_type : *header_values_type) {
-            auto& name = header_type.first;
-            auto& header_data_type = header_type.second;
+    for (const auto& header_type : header_values_type_) {
+        auto& name = header_type.first;
+        auto& header_data_type = header_type.second;
 
-            size_t bytes_size_per_frame = header_data_type.value_shape * header_data_type.value_bytes_size;
-            size_t buffer_size_bytes = n_images * bytes_size_per_frame;
+        size_t bytes_size_per_frame =
+                header_data_type.value_shape * header_data_type.value_bytes_size;
+        size_t buffer_size_bytes = n_slots_ * bytes_size_per_frame;
 
-            shared_ptr<char> buffer(new char[buffer_size_bytes](), std::default_delete<char[]>());
-            metadata_buffer.insert({name, buffer});
-            metadata_length_bytes.insert({name, bytes_size_per_frame});
-        }
+        shared_ptr<char> buffer(
+                new char[buffer_size_bytes](), std::default_delete<char[]>());
+
+        metadata_buffer.insert({name, buffer});
+        metadata_length_bytes.insert({name, bytes_size_per_frame});
     }
 }
 
-void MetadataBuffer::add_metadata_to_buffer(string name, uint64_t frame_index, const char* data)
+void MetadataBuffer::add_metadata_to_buffer(
+        const string& name,
+        const uint64_t frame_index,
+        const char* data)
 {
-    if (frame_index >= n_images) {
-        stringstream error_message;
-        using namespace date;
-        error_message << "[" << std::chrono::system_clock::now() << "] ";
-        error_message << "Requested frame_index " << frame_index << " ";
-        error_message << "for metadata " << name << " in metadata buffer is out of range. ";
-        error_message << "Number of available slots: " << n_images << endl;
+    if (frame_index >= n_slots_) {
+        stringstream err_msg;
 
-        throw runtime_error(error_message.str());
+        using namespace date;
+        using namespace chrono;
+        err_msg << "[" << system_clock::now() << "] ";
+        err_msg << "[MetadataBuffer::add_metadata_to_buffer]";
+        err_msg << " Requested frame_index " << frame_index ;
+        err_msg << " is out of range.";
+        err_msg << " Available n_slots_ " << n_slots_ << endl;
+
+        throw runtime_error(err_msg.str());
     }
 
     auto metadata = metadata_buffer.find(name);
 
     if (metadata == metadata_buffer.end()) {
-        stringstream error_message;
-        using namespace date;
-        error_message << "[" << std::chrono::system_clock::now() << "] ";
-        error_message << "Cannot add data to metadata buffer because '" << name << "' is not declared."<< endl;
+        stringstream err_msg;
 
-        throw runtime_error(error_message.str());
+        using namespace date;
+        using namespace chrono;
+        err_msg << "[" << system_clock::now() << "] ";
+        err_msg << "[MetadataBuffer::add_metadata_to_buffer]";
+        err_msg << " Undeclared header metadata " << name << endl;
+
+        throw runtime_error(err_msg.str());
     }
 
     size_t bytes_size_per_frame = metadata_length_bytes.at(name);
@@ -54,7 +67,7 @@ void MetadataBuffer::add_metadata_to_buffer(string name, uint64_t frame_index, c
     char* buffer = metadata->second.get();
     buffer += buffer_offset;
 
-    memcpy(buffer, data, bytes_size_per_frame); 
+    memcpy(buffer, data, bytes_size_per_frame);
 }
 
 shared_ptr<char> MetadataBuffer::get_metadata_values(string name)
@@ -62,23 +75,26 @@ shared_ptr<char> MetadataBuffer::get_metadata_values(string name)
     auto metadata = metadata_buffer.find(name);
 
     if (metadata == metadata_buffer.end()) {
-       stringstream error_message;
-       using namespace date;
-       error_message << "[" << std::chrono::system_clock::now() << "] ";
-       error_message << "Cannot get data from metadata buffer because '" << name << "' is not declared."<< endl;
+       stringstream err_msg;
 
-       throw runtime_error(error_message.str());
+       using namespace date;
+       using namespace chrono;
+       err_msg << "[" << system_clock::now() << "] ";
+       err_msg << "[MetadataBuffer::get_metadata_values]";
+       err_msg << " Undeclared header metadata " << name << endl;
+
+       throw runtime_error(err_msg.str());
     }
 
     return metadata->second;
 }
 
-shared_ptr<unordered_map<string, HeaderDataType>> MetadataBuffer::get_header_values_type()
+const MetadataBuffer::header_map& MetadataBuffer::get_header_values_type()
 {
-    return header_values_type;
+    return header_values_type_;
 }
 
-uint64_t MetadataBuffer::get_n_images()
+uint64_t MetadataBuffer::get_n_slots()
 {
-    return n_images;
+    return n_slots_;
 }
\ No newline at end of file