Short answer: Both Microsoft GCC High and AWS GovCloud (US) meet FedRAMP Moderate and are acceptable for CUI under DFARS 252.204-7012. For a small contractor, GCC High wins on day-one productivity (M365, Teams, SharePoint in one bundle) but locks you into Microsoft and typically costs $40–$60 per user per month. AWS GovCloud wins on infrastructure flexibility, lower idle cost, and multi-cloud freedom — but you bring your own collaboration stack. Most sub-50-person shops should pick GCC High for the office side and AWS GovCloud for any custom apps or engineering data.
Compliance parity
Both platforms hold FedRAMP High authorizations and are explicitly named in DoD's December 2023 Moderate Equivalent memo as acceptable for CUI. Both publish a customer responsibility matrix (CRM) you'll cite in your SSP. From a "can I legally store CUI here" standpoint, this is a tie.
Real cost comparison
GCC High
- M365 E3 GCC High: ~$36/user/month
- M365 E5 GCC High: ~$57/user/month
- One-time tenant migration: $3k–$15k via partner
- Minimum seat counts and partner-only purchasing add friction
AWS GovCloud
- No per-user minimum — pay for what you provision
- ~20–25% premium over commercial AWS for the same instance types
- You bring email, chat, and file sharing (not bundled)
- Data transfer between commercial and GovCloud regions costs egress fees
Productivity & collaboration
GCC High is the default answer for email, document collaboration, and Teams meetings on CUI. Outlook, Word, Excel, SharePoint, OneDrive, and Teams are all in-tenant, and in-scope. AWS GovCloud has no equivalent productivity suite — you'd pair it with WorkMail (limited) or run GCC High alongside.
Engineering & custom workloads
AWS GovCloud is the better home for: CAD/PLM systems handling drawings, custom SaaS your team builds, build pipelines that touch CUI source code, and any workload needing GPU, containers, or serverless compute. Azure Government is the AWS GovCloud analogue and is also fine — pick based on your team's existing stack.
Recommendation by company shape
- 5–25 people, mostly office/email CUI: GCC High only.
- 10–50 people with engineering data: GCC High for office + AWS GovCloud (or Azure Government) for the engineering enclave.
- Software-only shop building DoD apps: AWS GovCloud or Azure Government with a minimal GCC High footprint for contract-handling email.
Frequently asked questions
- Can I use regular Microsoft 365 commercial for CUI?
- No. Commercial M365 is FedRAMP Moderate but does not meet DFARS 7012's incident-reporting and media-preservation requirements. You need GCC High (or GCC for FCI-only).
- What about Google Workspace?
- Google Workspace has FedRAMP High Assured Workloads, but adoption in the DoD supply chain is still small. Most primes default to expecting GCC High or AWS/Azure Gov.
- Do I have to migrate everything at once?
- No. Most contractors carve out a CUI enclave first (a single GCC High tenant or a single GovCloud VPC), keep non-CUI work in commercial, and grow the enclave as needed.
- Is GCC High overkill if I only have one CUI contract?
- Often yes for a single small contract. Look at AWS GovCloud + Datto/Egnyte for files, or a managed CMMC enclave service, before committing to a full M365 GCC High migration.
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