AJAX + PHP + MongoDB Performance on Amazon AWS

Lets say I had the following scenario:

• Amazon AWS EC2 large server


• Mongodb collection with 100000 documents


• 10 AJAX calls per second to a PHP script that takes post data and updates one document from that collection. That document is updated using mongo update().

Am I going to run into performance issues? Do I need to figure out some other way to do this?

Basically I'm using AJAX to send new data to update a collection when a user makes a change to a page.

One solution I thought of is making an array of changes that user makes and then letting the user commit all of those changes at the end (similarly to how submitting a form works), but it'd be nice to know I had the option of just making the 10 calls per second.