PHP/MySQL Optimization and customization expert for custom Instagram script

I have a custom script that works with the Instagram API that sends notifications when subscribed users post a new picture. I need assistance optimizing the code and adding features. I require someone that speaks fluent english, and has experience working with large databases. The database is a few hundred megabites, and the server makes millions of queries per day. Programmer must have knowledge of Instagram and its API. VPS: Xeon 2.5ghz 6 cores , 3gig Ram , Site: 800+ members, 50,000+ media entries DB Size 300mb Problem: MySQL is consuming too much processing power. Every 10 min, the script crawls everyone's profiles to see the last 3 pictures posted. For each user, it then it checks the 50,000+ media ids to see if the 3 pictures exist. If not, they are considered new pictures, and they are then added to the db. Needed* : At least 3yrs Experience with PHP/Mysql : Experience in Optimize PHP coding and Mysql DB's for performance and speed : Prior work and experience with Large DBs