AWS KMS SLA Credits & Refunds

KMS outages cost engineering teams twice: once in lost productivity, and again in unclaimed service credits sitting on the table because nobody filed a ticket in time. Here's how the KMS SLA actually works, what AWS will and won't credit you for, and how teams are automating the claim process end-to-end.

What this guide covers

• The official AWS KMS uptime commitment and credit tiers
• Which incidents qualify (and which exclusions silently disqualify claims)
• How to file a KMS credit request inside the AWS claim window
• Why manual claim recovery typically leaves money on the table

Frequently asked questions about AWS KMS SLAs

What is the typical SLA uptime guarantee for AWS KMS?

AWS KMS carries one of the highest commitments on the platform: a 99.999% Monthly Uptime Percentage per region (roughly 26 seconds of allowable downtime per month). Service credits scale at 10% (99.0-99.999%), 25% (95.0-99.0%), and 100% (below 95.0%) of monthly KMS charges.

How do I claim AWS KMS SLA credits after an outage?

Open a billing case in the AWS Support Center within 60 days of the affected billing period (the exact window is in the KMS SLA itself). The case needs: the affected resource IDs, timestamps of the disruption in UTC, your monitoring evidence (CloudWatch metrics, error logs, or third-party uptime monitoring) cross-referenced against the AWS Health Dashboard, and your calculation of the Monthly Uptime Percentage. AWS reviews the case manually and applies any granted credit to your next invoice rather than refunding cash. Teams that file these regularly automate the evidence-gathering step because it's the most error-prone — a claim missing the wrong field gets denied and has to be refiled.

What exclusions apply to the AWS KMS SLA?

KMS specifically excludes throttling caused by exceeding the per-account request-rate quota on cryptographic operations, as well as failures from customer-managed CloudHSM-backed custom key stores — those are customer infrastructure issues, not KMS unavailability.

Why is it difficult to get refunds for KMS outages manually?

Security and identity services fail quietly. A KMS disruption may not crash anything visible — it just causes authentication latency, silent permission denials, or policy-propagation delays that surface as user-reported bugs. Proving an SLA breach for KMS requires logs that capture these symptoms at request granularity, which most teams don't retain by default.

Related AWS SLA guides

Other AWS services that share the same claim window and Support Center workflow:

• AWS IAM SLA credits — Security
• AWS EC2 SLA credits — Compute
• AWS S3 SLA credits — Storage
• AWS RDS SLA credits — Database

Stop leaving AWS credits unclaimed

The hardest part of recovering KMS credits isn't the SLA — it's the lag between an outage and the moment somebody on your team has the bandwidth to file the case. By the time the FinOps team gets around to it, the evidence has rolled out of CloudWatch and the billing window is closing.

Next Signal watches AWS Health and your own observability data, detects KMS SLA breaches in real time, assembles the evidence package the way AWS expects it, and files the billing case for you. See how it works or start a free trial.