In general, we have optimized the app to be as integrated with Microsoft Teams as possible. The result of this is that the architecture for Cloud & Server/DC is very similar. This is a bit uncommon for the on-premise systems, as traditional apps for these systems are not relying on any cloud service. To provide the same features for Jira Server & Data Center as well, there is currently no other way than using a cloud infrastructure.
High level architecture / data flow
All service connections are done via our cloud backend - same as for any other Jira Cloud app on the Atlassian Marketplace. The following diagram shows the high-level architecture. Microsoft Teams does not allow connecting to Jira directly, therefore all connections to and from Microsoft Teams have to go through our servers.