What is the problem with synchronous interaction under high load?

The problem of synchronous interaction under high load is that each request blocks the thread until a response is received, which leads to:

• Delays and increased response times if the server cannot process all requests quickly.
• Scalability limitations, as the number of requests processed simultaneously is limited by the number of threads.
• The risk of deadlocks and performance degradation during peak loads.

For example, in a web application, a synchronous call to an external service will cause each user request to wait for a response, blocking server resources. With a large number of users, this can lead to resource exhaustion and service denial.

To address this, asynchronous approaches, message queues, or horizontal scaling are often used.