Event ID 12002 and 12032: WSUS web services stop answering and clients stall
Event ID 12002 and 12032 with HTTP 503 mean the WSUS application pool has stopped. Restart WsusPool and raise its limits to bring clients back.
HTTP 429 and HTTP 503 in SharePoint Online: throttling and list limits
HTTP 429 and HTTP 503 mean SharePoint Online is throttling your requests or a list is over threshold. Learn how to back off, batch and index properly.
HTTP 500 on Microsoft-Server-ActiveSync: every mobile device stops syncing
HTTP 500 and 503 on Microsoft-Server-ActiveSync stop every device at once. Learn how to read Event ID 1008 and get the virtual directory healthy.