title: What is the purpose of the ConcurrencyStamp column in the AspNetUsers table in the new ASP.NET MVC 6 identity?
body: <p>What is the purpose of the <code>ConcurrencyStamp</code> column in the <code>AspNetUsers</code> table in the new ASP.NET MVC 6 identity?</p>
  
  <p>This is the database schema of the <code>AspNetUsers</code> table:</p>
  
  <p><a href="https://i.stack.imgur.com/Zr319.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Zr319.png" alt="enter image description here"></a></p>
  
  <p>It is also there in the <code>AspNetRoles</code> table:</p>
  
  <p><a href="https://i.stack.imgur.com/6Lbwx.png" rel="noreferrer"><img src="https://i.stack.imgur.com/6Lbwx.png" alt="enter image description here"></a></p>
  
  <p>As I remember it wasn't there in the ASP.NET MVC 5 identity.</p>
  
  <p>What I've noticed so far is that it seems to have GUID values as it is defined with the following code:</p>
  
  <pre><code>/// &lt;summary&gt;
  /// A random value that must change whenever a user is persisted to the store
  /// &lt;/summary&gt;
  public virtual string ConcurrencyStamp { get; set; } = Guid.NewGuid().ToString();
  </code></pre>
  
  <p>But this documentation is not sufficient for me to understand in which situations it is used.</p>