Here so called Service Application indicate to background daemon for application such like Request Handle Server, Flow Processor. In Cloud Era, every Service Application should consider these three feature into fundamental design:
1. High Availability: HA has three design level based on the complication and cost. Lowest level is none. Basic Level is Active-Standby. The highest level is Capacity Impact. To reach the Highest Level, it means your system has some kind of scale out ability. However, we have met some terrible design which doesn't control the database transaction and lock logic well. That will introduce incapable to scale out your application and limited your option to Active-Standby Design. Otherwise, all well trained developers should have the ability to implement the application with scale out.
2. Application Resilient: any application would happen the process crash or machine incidentally rebooted. There should be a design to make the service resiliently restarted or elegantly terminated and started by other application. This is not only about the exception handle issue but also the service continuity. However, most modern designed OS has the basic tool to keep this feature on your application.
3. Log Notification: This is must have but each team has different implementation.
