The synchronous access pattern works in the opposite manner to the asynchronous pattern. Instead of forwarding the request and forgetting about the response, the synchronous access pattern makes a request and then waits for the response to be generated by the other application.

This kind of pattern is usually followed in the case of federated integration, where the middleware acts as a intermediate, handling the access to the backend applications it's managing.

For example, inside a gateway-based pattern, the middleware usually takes up the request, forwards the request to the backend application, and then waits for the response to arrive, before moving on to the next request.

These were just a few basic patterns that govern the process of EAI. There are close to 65 EAI patterns that are still in use that facilitate the concept of EAI.

Now, let's take a look at some of the common issues that prevent a successful integration between the different enterprise applications.