For high traffic websites we recommend the following software and configurations:
- Use a high performance cache backend for Pimcore (Redis2 is recommended).
- Enable the output-cache in Settings > System.
- Install and setup varnish cache (Pimcore sends already the right headers for varnish => ouput-cache lifetime, ... ).
- Only use sessions when really necessary. The Pimcore Output-Cache detects the usage of sessions in the code and disables itself if necessary.
- Tuning your MySQL configuration to exactly fit the needs of your application.
- Make use of in-template caching.