Realpath cache caches the real file system paths of filenames referenced instead of looking them up each time. Every time various file functions are performed or require a file and use a relative path, PHP has to look up where that file really exists.
To improve Commerce performance, use the following recommended settings to configure the
realpath_cache settings in the
For configuration instructions, see How to set PHP options.
If the Realpath cache configuration values are too low or too high, it adds additional overhead during cache generation which slows performance.