Using MySQL replication gives you an opportunity to scale out read queries. However, MySQL replication is asynchronous; the slave may fall behind.
This Wednesday, January 23 2013, I'll be presenting a free webinar about using MySQL replication on busy PHP web sites. Register here: http://www.percona.com/webinars/readwrite-splitting-mysql-and-php
Applications have variable tolerance for data being out of sync on slaves, so we need methods for the application to query slaves only when their data are within tolerance. I describe the levels of tolerance, and give examples and methods for choosing the right tolerance level in your application.
This talk shows the correct ways to check when the slave is safe to query, and how to architect your PHP application to adapt dynamically when the slave is out of sync.
I'll also demonstrate an extension to the popular PHP Doctrine database access library, to help application developers using MySQL to make use of read slaves as effectively as possible.
Please join me in this free webinar this Wednesday!