Up to version 8, you had to use additional extensions such as realUrl or Cooluri for readable URLs (search engine friendly URLs). These have created their own database tables and additional configuration. No question, especially realUrl has served well for many years and has also been used on large and complex websites. Also I have used realUrl and would like to express once again my thanks to the developer.
Since version 9 everything has changed. The handling of readable URLs, in short "slugs" is now integrated directly into the core. This eliminates not only the extra configuration of third-party extensions, but also a lot of ballast in the program structure and the structure of the pages. If you create a very simple template for testing purposes, test it in TYPO3 version 8 with realUrl and then in version 9, you can see the enormous difference in speed.
Brand new since version 9.5 is the backend module "Redirects". This makes it easy to set up SEO redirects in the backend. The savvy SEO professional may swear by his manually created .htaccess file. But this feature in the new TYPO3 is really good and works smoothly. Although it does not bring direct performance benefits, but according to previous own experiences also no disadvantages. Even if the option "hitCount" is activated. It counts the clicks for all SEO redirects and displays them in the backend.
Also new in TYPO3 is the integrated sitemap functionality, which is provided by the included extension "seo". In the site settings, the sitemap can be activated in a few simple steps.
These new features can be customized in the backend of TYPO3 v9 under "Settings" by an administrator. Only 2 of them are crucial for the speed of TYPO3.
If this option is enabled, the deprecated "pages_language_overlay" table is no longer used, speeding up the system.
When this option is enabled, backend module controller actions and eID scripts do not receive an out-of-date prepared response object as the second argument. Enabling this feature will slightly improve performance.
For new TYPO3 installations, the developer team recommends that you enable these new features from the beginning:
My personal conclusion: TYPO3 is now faster and more practical than ever. From my point of view, the new core feaures "Slugs, Sitemap, Meta / SEO", as well as the enormous speed improvement make the CMS a whole lot more interesting. This is i.a. Another reason why I decided at the beginning of 2019 to work only with TYPO3. For me, it's the most powerful tool for special web applications, especially for multilingual content and high user management and scalability requirements.