Cost Allocation
Attributing spend to the team, service or customer that causes it — the prerequisite for every other cost conversation.
Definition
Cost allocation maps spend to something accountable: a team, a product, a service, a tenant. Without it, cost is an undifferentiated total that nobody owns and everybody defends.
Why it must come first
Every cost optimisation conversation stalls on "whose is this?" Without allocation:
- Nobody knows whether a resource is still needed, so nothing is deleted.
- Optimisation is done centrally by people without context, who are correctly resisted.
- Nobody can be given a budget, so nobody has an incentive.
- The largest inefficiencies hide in the unattributed pool.
Allocation is not itself valuable — it is what makes everything after it possible. This is why it ranks above optimisation in any remediation plan.
How to do it
- Mandatory tags enforced at creation, not requested. A resource without an owner tag should fail to deploy. Retrofitting attribution onto thousands of untagged resources is a project nobody funds, which is why enforcement must be preventive.
- Account or subscription boundaries per team or environment, which is the strongest and simplest allocation mechanism and does not depend on tag discipline at all.
- Shared costs allocated by a stated rule, not left unattributed. Networking, observability, platform teams and shared clusters must be apportioned — by usage where measurable, by an agreed key otherwise. Publishing the rule matters more than its precision.
- Cost per business unit, not just per team. Cost per tenant is what makes pricing decisions possible and reveals unprofitable customers.
The organisational half
Allocation without visibility changes nothing. Teams need to see their own spend, regularly, in a form they can act on — ideally next to their unit cost so they can see efficiency rather than just magnitude. And someone must be accountable for the number.
Failure scenarios
- Tags optional, so coverage is 60% and the untagged 40% is where the waste is.
- Shared costs unallocated, so a third of spend has no owner.
- Allocation reported to finance and not to engineers, so the people who can act do not see it.
- No cost per unit, so a team that grew efficiently is criticised alongside one that did not.
Interview question
"Forty percent of your cloud spend is untagged. What do you do?"