feat: Added example for how to use row level security to implement TTL

web/docs/guides/auth.mdx

@@ -248,6 +248,31 @@ create policy "Only Blizzard staff can update leaderboard"
   );
 ```
 
+### Time to live for rows
+
+Policies can also be used to implement TTL or time to live feature that you see in Instagram stories or Snapchat. 
+In the following example, rows of `stories` table are available only if they have been created within the last 24 hours. 
+
+```sql
+-- 1. Create table
+create table if not exists stories (
+  id uuid not null primary key DEFAULT uuid_generate_v4(),
+  created_at timestamp with time zone default timezone('utc' :: text, now()) not null,
+  content text not null
+);
+
+-- 2. Enable RLS
+alter table stories 
+  enable row level security;
+
+-- 3. Create Policy
+create policy "Stories are live for a day"
+  on stories
+  for select using (
+    created_at > (current_timestamp - interval '1 day')
+  ); 
+```
+
 ### Advanced policies
 
 Use the full power of SQL to build extremely advanced rules.