Synchronous and asynchronous interactions: differences, when to choose, what is polling?

Synchronous interaction is when the requester waits for a response, blocking until it is received. It is simple and understandable, but can lead to delays and blocking if the response takes a long time.

Asynchronous interaction is when the requester does not wait for an immediate response but continues working. The response is processed later, usually via callback, event, or message queue. This increases responsiveness and scalability but complicates the logic.

Polling is a method of asynchronous interaction where the client periodically polls the server or resource to check if the response is ready or if the data has changed. For example, the client sends a request every 5 seconds to check the status of a task.

When to choose:

• Synchronous — when simplicity and quick response are important, and delays are minimal.
• Asynchronous — when operations are long, it is necessary not to block the thread or UI, or when the system is distributed.
• Polling — when push notifications or events cannot be used, but it is necessary to periodically check the status.