diff --git a/ADVANCED.md b/ADVANCED.md
index 35459eb..61fd3bb 100644
--- a/ADVANCED.md
+++ b/ADVANCED.md
@@ -40,4 +40,13 @@ To identify different services currently running, refer to the "SERVICE" column
 docker-compose ps
 ```
 
-![services](https://i.ibb.co/ZXG3Ld9/image.png)
\ No newline at end of file
+![services](https://i.ibb.co/ZXG3Ld9/image.png)
+
+## RLN - Rate Limit Nullifier
+
+RLN is the technology used to achieve the rate limiting feature, which combines zero-knowledge
+proofs, hashing, Merkle tree, Blockchain, etc.
+
+Deeper technical details can be found in:
+[RLN-V1 spec](https://rfc.vac.dev/spec/32/)
+[RLN-V2 spec](https://rfc.vac.dev/spec/58/)