Should we prefer existing Azure Services or build new from scratch ?

Azure offers hundreds of services which perform various tasks. When we are designing architecture of cloud based systems then we have 2 options:

1. Use an existing Azure service.

2. Build a new one from scratch

As a general rule of thumb, it is usually a better option to use an existing Azure service instead of building one from scratch.

Reason for using existing Azure services:

Built-in Azure services offer better SLA, automation, scaling, security, monitoring and many other useful features. If we have to implement these features in our custom implementation then it will take more time and efforts. Lets see an example where we will discuss efforts in using existing Azure service and building a custom one from scratch through manual setup:

Example : Run Web API to copy data from some file to database.

Please note that built-in services are not always the best option.

For example, we can not access registry of machine using Azure functions, for this we need to setup virtual machine and deploy Web API code.