Alright, let's get this over with. I see the "just pull the CUR" advice tossed around like it's a magic wand that instantly reveals all cloud spending sins. Having been handed more of these monstrous CSV exports than I care to remember—usually after some VP panics about a bill spike—I can tell you it's more like being handed the raw census data for an entire country and being asked "so, why is our population aging?"
The CUR isn't an answer. It's the raw material from which you might, with considerable effort, forge an answer. Think of it as the itemized receipt from a grocery store the size of a city, where every single item you bought is listed, but in 200 different languages, using product codes only the vendor understands.
So, you've downloaded the CUR. You open it in Excel and it immediately groans. Here's what you're actually looking at:
* **The `line_item_line_item_description` column is your best friend and worst enemy.** It's the human-readable-ish text for the charge. Start here to get a vague sense of what a charge is for ("$0.005 per EC2 EBS:gp3 Volume Storage (USW2-AZ2)").
* **The `product_product_name` column is the vendor's official category.** This is where you'll see "Amazon Elastic Compute Cloud" or "Amazon Relational Database Service."
* **The `resource_id` column is the specific thing that cost you money.** This is the EC2 instance ID (i-0abcd1234...), the EBS volume ID (vol-5678...), etc. This is the hook you need to tie a cost to an actual asset in your environment.
* **The `line_item_usage_type` column is the *how*.** This is the granular detail—"EU-BoxUsage:c5.2xlarge" or "EBS:VolumeP-IOPS.piops". This tells you not just that it's EC2, but the specific size and operation.
* **The `line_item_blended_rate` and `line_item_unblilled_cost` are where the rubber meets the road.** This is the rate applied and the calculated cost for that line item.
The immediate problem you'll face is volume. A modest AWS account can generate tens of thousands of lines per day. Your first job is to filter and pivot. Ignore the $0.00 test lines. Filter to a specific service (`product_product_name`) or linked account (`line_item_usage_account_id`). Then, start asking specific questions: "What is my single most expensive RDS instance this month?" Filter to RDS, group by `resource_id`, sum the cost.
The real work begins when you try to make sense of it. That `line_item_usage_type` of "APE1-EBS:SnapshotUsage"? Good luck knowing which team's snapshots those are without cross-referencing tags (and pray your tagging is actually enforced). The CUR will tell you *what* you spent, but rarely *why*. That requires organizational context—a missing piece in most "just analyze the CUR" hot takes.
My advice? Don't start with the raw CSV. Use Cost Explorer's built-in reports to get a high-level view first. Identify the biggest cost drivers (EC2, Data Transfer, etc.), *then* use the CUR to surgically investigate those specific areas. Otherwise, you'll drown in data before you find a single actionable insight.
-- Carl
Test the migration.