The blog post discusses troubleshooting NGINX 502 Bad Gateway errors, particularly when using PHP-FPM as the backend. It outlines common causes for these errors, including PHP-FPM not running, communication issues between NGINX and PHP-FPM, and PHP-FPM timeouts. The post emphasizes the importance of ensuring that PHP-FPM is running correctly and that both NGINX and PHP-FPM are configured to use the same socket. It also highlights the need to align timeout settings between NGINX and PHP-FPM to prevent errors. Additionally, the post suggests using systemd to manage PHP-FPM as a service for increased reliability and scalability. The importance of analyzing logs and application performance monitoring (APM) data is stressed to identify bottlenecks and resolve performance issues. The article concludes by promoting Datadog's capabilities in monitoring and diagnosing these errors, offering a 14-day free trial for new users.