Always we assume that all the External Systems will meet SLAs
all messages should be constructed and sent to the IP address of the API server in a specified amount of time
Separate into two parts
1. Message construction at your application
2. Sending the message to external system
Message construction at your application
How your architecture supports the construction of a message within SLAs
Example:
You need some data from database, the same can be achieved by caching the data and retrieving from it.
If there is any design
pattern helps to improve the performance
Based on Sud requirement using asynchronous queues for constructing the message
Because of Clustered environment: meeting the SLAs criteria as load increases
External Systems
Example
Based on Sud requirement if possible you can define asynchronous communication with external systems and you are not holding your application resources for response. Incase external system is slow in processing the request it will not impact your application if it is asynchronous (depends Sud requirements)