diff --git a/doc/install/requirements.md b/doc/install/requirements.md
index 9f7c03badcf93c76f02d9901e4c1b81707549d0f..ccfa670565e38a8a29e292cd6841a8b2af529e6c 100644
--- a/doc/install/requirements.md
+++ b/doc/install/requirements.md
@@ -84,7 +84,15 @@ If you have enough RAM memory and a recent CPU the speed of GitLab is mainly lim
 
 ## Database
 
-If you want to run the database separately, the **recommended** database size is **1 MB per user**
+If you want to run the database separately, the **recommended** database size is **1 MB per user**.
+
+## Redis and Sidekiq
+
+Redis stores all user sessions and the background task queue.
+The storage requirements for Redis are minimal, about 1kB per user.
+Sidekiq processes the background jobs with a multithreaded process.
+This process starts with the entire Rails stack (200MB+) but it can grow over time due to memory leaks.
+On a very active server (10.000 active users) the Sidekiq process can use 1GB+ of memory.
 
 ## Supported webbrowsers