In what cases should synchronous interaction between microservices be used?

Synchronous interaction between microservices should be used when:

• An immediate response is required to continue operation (e.g., data request for user display).
• Operation sequence is important, and the next step depends on the result of the previous one.
• Data consistency in real-time needs to be ensured.

Example: an authentication service that must confirm the user before proceeding with further actions.

However, synchronous interaction increases coupling and can lead to delays, so it should only be used when necessary.