Merge pull request #743 from snaka/doc/cache-warning

docs: add cache invalidation warning for Redis Caching

Author: andrehjr

README.md

@@ -762,7 +762,10 @@ Split.redis = split_config[Rails.env]
 
 ### Redis Caching (v4.0+)
 
-In some high-volume usage scenarios, Redis load can be incurred by repeated 
+> [!WARNING]
+> The caching mechanism has known issues in multi-process environments (e.g., Puma) and multi-server deployments with load balancers (typical production environments). Cache invalidation does not propagate across processes or servers, which can lead to inconsistent experiment data being served to users. See [#735](https://github.com/splitrb/split/issues/735) for details. Use with caution in production environments.
+
+In some high-volume usage scenarios, Redis load can be incurred by repeated
 fetches for fairly static data.  Enabling caching will reduce this load.
 
  ```ruby