In order to make your CRM workflows perform best, you need to understand the difference between synchronous and asynchronous workflows so you can choose which is appropriate for your applications.
Synchronous workflows are a new feature that was introduced in Dynamics CRM 2013. Unlike asynchronous workflows which are sent to a queue, synchronous workflows execute in a single transaction.
This means you can eliminate the need for many plug-ins which were created for previous versions of Dynamics CRM.
You may want to disable synchronous workflows during import operations, because they will could be triggered by each new record and significantly slow down the import process.