What were the synchronous and asynchronous integrations? In which cases are each used? What is the danger of synchronous interaction?

Synchronous integrations assume that the calling system waits for a response from the called system until the operation is complete. Example: a REST API call where the client waits for an HTTP response.

Asynchronous integrations do not require an immediate response — the request is sent, and the system continues to work, with the response arriving later, for example, via a message queue (RabbitMQ, Kafka).

When to use:

• Synchronous integrations are suitable when a quick response is needed and the subsequent logic depends on the result (e.g., payment verification).
• Asynchronous are used if the operation is lengthy, an instant reaction is not critical, or there is a need to increase fault tolerance and scalability.

Dangers of synchronous interaction:

• Dependence on the availability and response speed of the external system, which can lead to blocking and reduced performance.
• Increased response time of the entire system.
• Risk of cascading failures if one of the services fails.