it depends on which kind of statistic you are looking for in a specific project. In a basic approach you might want to query the amount of issues (maybe extended by the criteria: 'last week'), the amount of blocker bugs and so on.
You also can use JQL in REST API calls.
Please find documentation on this here along with some examples.
In case of specific questions I am sure somebody here in Community will be able to catch up on this.
I have multiple projects that use variations of the same base workflow. The variations depend on the requirements of the project or issue type. The variations mostly come in the form of new statuses ...
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