Adding 'Addictional Information for Rate Limiting' sub section.

README.md

@@ -388,7 +388,13 @@ Maps are not safe for concurrent use: it's not defined what happens when you rea
 
 So, to get around this, we'll need to synchronize access to the map of rate limiters using a [sync.Mutex](http://golang.org/pkg/sync/#Mutex) (a mutual exclusion lock), so that only one goroutine is able to read or write to the map at any moment in time.
 
-**Important**: How mutexes work, and how to use them, can be quite confusing if you haven't encountered them before and it's impossible to fully explain in a few short sentences. A much more detailed article is available here - [Understanding Mutexes](https://www.alexedwards.net/blog/understanding-mutexes) - which provides a proper explanation. If you're not already confident with mutexes, I highly recommand reading this before you continue.
+**Important**: How mutexes work, and how to use them, can be quite confusing if you haven't encountered them before and it's impossible to fully explain in a few short sentences. A much more detailed article is available here - [Understanding Mutexes](https://www.alexedwards.net/blog/understanding-mutexes) - which provides a proper explanation. If you're not already confident with mutexes, I highly recommend reading this before you continue.
+
+#### Additional Information for Rate Limiting
+
+**Distributed applications** : Using this pattern for rate-limiting will only work if your API application is running on a single-machine. If your infrastructure is distributed, with your application running on multiple servers behind a load balancer, then you'll need to use an alternative approach.
+
+If you're using HAProxy or Nginx as a load balancer or reverse proxy, both of these have built-in functionality for rate limiting that it would probably be sensible to use. Alternatively, you could use a fast database like Redis to maintain a request count for clients, running on a server which all your application servers can communicate with.
 
 ### Performance