Common Causes:

• Not monitoring all information and system.
• Not processing the pending queue requests after recovering the system.
• Missing failover plan.

Points to be considered:

• Identify ways to detect failures and automatically initiate a failover, or redirect load to a spare or backup system.
• Consider implementing code that uses alternative systems when it detects a specific number of failed requests to an existing system.
• Consider how you can take the system offline but still process pending queue requests.
• Implement store and forward or cached message-based communication systems that allow requests to be stored when the target system is unavailable, and replayed when it is online.