Designing a Thread-Safe, High-Performance Logging System in Modern C++ (C++17/20)

I’m currently working on a medium-sized C++ project where I need to implement a custom logging system. The requirements go beyond basic logging, and I’d like to validate my design decisions before going too far.

Context

The logger is intended to be:

Thread-safe (used across multiple worker threads)

Low-latency (minimal blocking in hot paths)

Flexible (support multiple output sinks like console and file)

Extensible (easy to add new log levels or sinks later)

Current Approach

Right now, I have:

A singleton-style global logger instance (getGlobalLogger())

A mutex-protected std::ostream-like interface

Optional file output using std::ofstream

Message formatting via std::stringstream

Example (simplified):

void Logger::log(const std::string& message) { std::lock_guard<std::mutex> lock(mutex_); if (file_out.is_open()) { file_out << message << '\n'; file_out.flush(); } std::cout << message << '\n'; }

I’m concerned that the global mutex in my logger may become a bottleneck under heavy multithreading.
Would switching to a lock-free queue with a dedicated logging thread significantly improve throughput in practice?