AWS Free Usage Tier experience

I've had an app in the wild for about 1.5 years.  I'm in pure maintenance mode so other than replying to user emails, I check out error reports, reviews, and download stats every couple months.  Occasionally, I'll peak into the persistence to see what the raw data is looking like (shout out to sdbtool!).  But it's been some time since I looked at how much resources I'm consuming on AWS.  I built this app thinking I would always fall in the Free Tier pricing level.

My AWS usage report tells me 2 things:

• I'm a very small fry.
• The AWS Free Usage Tier is pretty generous.

Before getting to the AWS stats, here's my use case.  I probably have only a couple hundred active users today.  I'm using AWS for SimpleDB persistence (no graph processing here!) so all the compute time is dedicated to CRUD with the database.  SimpleDB rows are attribute-value pairs (Strings) and I average around half-a-KB of data per row.  I have about 25k rows of data in my SimpleDB instance.

My SimpleDB usage for July 2012:

• 0.052 Compute-Hours (25 free)
• 0.000529 GB-Month of storage (1 GB-Month free)

I was confused by the GB-Month number.  I thought that meant how much data I'm storing in my SimpleDB instance but it must refer to the amount of new data.  So that's half a MB of new data coming in which translates to around 1,600 new items ('rows' in SimpleDB parlance) in my domains (SimpleDB's word for 'tables') in July.  In fact, the total amount of disk space is represented by the TimedStorage-ByteHrs field of the detailed usage report.

My AWS usage for July 2012:

• 0.001 GB data transfer in (1 GB free)
• 0.002 GB data transfer out (1 GB free)

Since I serve up much more data than I ingest, the data out number is my only concern.  That's 2 MB of data leaving AWS and my app is fielding about 18K Select requests for items (SimpleDB's term for 'rows') each month.  Note the request might not be for an entire item - it could be for 1 or more attributes ('columns').

Add these numbers up and I obviously have room to scale!  In fact, I could get almost a 500x increase in activity and still fall within the free usage tier.  Since I only coded this app for fun and experience, I probably won't grow but it's fun to know where I'm at.  It's really exciting to consider all the backend options out there for developers (GAE is similarly generous).