docs: Fix caching docs to comply with current features.

docs/caching/README.md

@@ -1,33 +1,27 @@
-## Object caching
+## Object Caching
 
-Object caching by turned on by default with following settings
+Object caching is on by default with following settings
 
- - Default cache size 8GB. Cache size also automatically picks
-   a lower value if your local memory size is lower than 8GB.
+ - Cache size is 50% of your RAM size. Caching is disabled
+   if your RAM size is smaller than 8GB.
 
- - Default expiration of entries happensat 72 hours,
-   this option cannot be changed.
+ - Expiration of each entries happen on every 72 hours.
 
- - Default expiry interval is 1/4th of the expiration hours, so
-   expiration sweep happens across the cache every 1/4th the time
-   duration of the set entry expiration duration.
+ - Garbage collection sweep of the expired entries happen every
+   1/4th the set expiration hours value (every 18 hours).
+
+NOTE: None of the settings can be configured manually.
 
 ### Behavior
 
 Caching happens on both GET and PUT operations.
 
 - GET caches new objects for entries not found in cache.
+  Otherwise serves from the cache.
 
-- PUT/POST caches all successfully uploaded objects.
+- PUT/POST caches all successfully uploaded objects. Replaces
+  existing cached entry for the same object if needed.
 
-In all other cases if objects are served from cache.
-
-NOTE:
-
-Cache is always populated upon object is successfully
-read from the disk.
-
-Expiration happens automatically based on the configured
-interval as explained above, frequently accessed objects
-stay alive for significantly longer time due to the fact
-that expiration time is reset for every cache hit.
+NOTE: Expiration happens automatically based on the configured
+interval as explained above, frequently accessed objects stay
+alive in cache for a significantly longer time on every cache hit.