# Migration Dual-Run Cost Worksheet (July 2026)

Steady-state TCO tools miss the gap between “current” and “prod on AWS.” Fill before you approve a migration budget.

## Parallel run

| Input | Value |
| --- | --- |
| New AWS env weekly cost (on-demand + managed) | $ |
| Legacy env weekly variable cost during parallel | $ |
| Planned parallel weeks (min 1; typical 2–4; regulated 8–12) | |
| **Parallel line item** = (AWS + legacy) × weeks | $ |

## One-time transfer

| Path | Volume | Notes | Est. $ |
| --- | --- | --- | --- |
| Internet ingress to AWS | TB | AWS ingress usually $0; check DC egress | |
| Snow Family / DataSync | TB | Verify current device + days pricing | |
| DMS replication instance × weeks | | Include CDC until cutover stable | |

## Day-1 “invisible” AWS

- [ ] CloudTrail data events (if enabled)
- [ ] Config recording
- [ ] GuardDuty
- [ ] VPC Flow Logs → prefer S3 over CloudWatch Logs
- [ ] MAP 2.0 tags activated if MAP-funded ([MAP checklist](/examples/architecture-blog-2026/map-smb/map-eligibility-partner-checklist.md))

## Cutover rule

Do **not** decommission legacy until ≥1 full business cycle on AWS with a tested DNS/DB rollback path.