/vip-config directory
The /vip-config directory contains a file named vip-config.php. Settings usually found in wp-config.php (e.g., to issue a very early redirect) should be added to this file instead. Not all settings can be changed, as VIP has optimized certain aspects of the WordPress install.
Most of WordPress is not available when this file is loaded. The inclusion of WordPress functions or plugin defined functions will most likely result in a fatal error for an undefined function. Code in this file should be limited to pure PHP.
API keys and secrets should not be stored in this file, and should be be defined by setting environment variables with VIP-CLI instead.
Caution
All updates made to vip-config.php should be tested in a non-production environment before deploying to production.
It is likely for fatal errors or syntax errors in this file to make an entire site or multisite unavailable.