I was reading about memcache and one of the questions that I have for this moment is about 'measuring database load'. In this tutorial they are talking about a 'database load of 20'.
How can I measure the database load of a web application?
That's a very random metric, as far as I am aware I haven't heard about any specific "load" unit measure for databases.
I highly suspect that "load 20" is very dependent on how that person in that tutorial has decided to define what "1 database load" is.
I could just say this database handles "20 kittens" and it would be as meaningful! :)
You need to come up with your own load metrics and definitions.
Create a stress test using Load Impact for example. Use a small amount of data.
Increase the amount of data, rinse and repeat:
(a) How well does your application scale as data increases?
Once you have created this baseline, you can then play with different databases optimisations and directly see the impact against your baseline, in essence this could be your "database load unit".