It is important to optimize website code for faster page load and for best practices standards especially when it comes to mobile and SEO. Unfortunately, Drupal is not optimized out of the box. I would to discuss performance optimization options such as configuration best practices, caching(server, code, datasources, database, etc..), hosting, etc... Here is a list of topics included:
Configuration Best Practices
Views Caching
System Administration
Cache Replacements
Cache and Optimize Specific Components
External Caching
Cache Warming / Priming
Services
Drupal-Specific Hosting
Tools