title: In what circumstances a REST API should return HTTP Status 503
body: <p>The standard says:</p>
  
  <p>10.5.4 503 Service Unavailable. The server is currently unable to handle the request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay.</p>
  
  <p>REF: <a href="https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html" rel="nofollow noreferrer">https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html</a></p>
  
  <p>If the server is having lock contension at the database access level, should the server return 503 in such cases. Or is the 503 status meant for:</p>
  
  <ul>
  <li>Network overload</li>
  <li>DOS type situations</li>
  <li>Maxed out load balancing</li>
  <li>Explicit maintenance window.</li>
  </ul>
  
  <p>What other circumstances it makes sense to return HTTP status 503.</p>
  
  <p>Any detailed clarification is much appreciated.</p>