doc: improve AsyncLocalStorage introduction

doc/api/async_hooks.md

@@ -973,6 +973,10 @@ chains. It allows storing data throughout the lifetime of a web request
 or any other asynchronous duration. It is similar to thread-local storage
 in other languages.
 
+While you can implement your own implementation on top of the `async_hooks`
+module, `AsyncLocalStorage` is a performant and memory safe implementation that
+involves non-obvious optimizations.
+
 The following example uses `AsyncLocalStorage` to build a simple logger
 that assigns IDs to incoming HTTP requests and includes them in messages
 logged within each request.