I usually build the inventory in the first week; it saves a lot of time later. The teams that skip this always pay for it in week three. A US to EU cloud migration inventory is the first real engineering task in any cross region move. If you skip it, every later decision is based on partial truth. A good inventory is not a spreadsheet for the sake of a spreadsheet. It is a shared view of what actually runs, who owns it, and where data lives today.
Start by listing every production workload with an owner, current environment, and criticality. Capture traffic patterns, peak usage, and any hard deadlines such as batch windows. Add all external dependencies, including SaaS, payment processors, identity providers, and data pipelines. If the team cannot explain how a service is deployed or updated, it is a migration risk and belongs in the inventory.
Data residency and dependency mapping: For every database, bucket, or queue, record the type of data inside it and the location where it is created, processed, and stored. Look for cross region data flows that happen through analytics, backups, or third party APIs. These often matter more than the primary workload location. If there are contractual constraints, attach them directly to the asset record so they are not lost in later planning.
Dependencies should be mapped in a way that supports migration waves. Note which services must move together and which can be isolated. For each dependency, capture protocol, authentication method, and latency tolerance. This creates the basis for migration sequencing, cutover planning, and rollback scenarios. If a dependency cannot tolerate latency changes, it likely needs a different migration path.
Include operational details that affect cutover. Record cron jobs, scheduled batch jobs, and data export windows. Identify manual steps that still happen outside the CI or IaC flow. These details often become the reason a cutover slips.
Inventory outputs that matter: The output should include a dependency map, a list of migration waves, and a risk register. Add a separate asset register for accounts, domains, certificates, secrets, and build pipelines. If you can, include last deployment date and last incident date. This turns the inventory into a living operational view, not a static list.
A practical inventory checklist for week one:
- List production accounts, subscriptions, and root identities.
- Export 90 days of billing and usage data for each workload.
- Capture all public endpoints and inbound integrations.
- Record data stores, backup locations, and retention settings.
- Identify data residency constraints and the decision owner.
- Document the current on call owner for each service.
After week one, you can deepen the inventory by adding cost attribution, current IaC coverage, and risk severity. This helps prioritize which services move early and which should wait. A complete inventory does not need to be perfect. It needs to be current enough to design a plan that you can rehearse and execute without surprises. This is the baseline that makes a US to EU cloud migration predictable.
Include non obvious assets such as CI runners, logging sinks, and third party monitoring accounts. These often hold keys or data flows that break when network topology changes. If you migrate workloads but leave build and monitoring systems in the old region, you will keep data residency risk. Capture data classification at a simple level even if you do not have a full taxonomy. Mark personal data, financial data, and operational telemetry. This makes it easier to decide what must move first and what can move later. It also speeds up legal and compliance review when questions appear.
The inventory should live in one place with a clear owner. If ownership is unclear, updates stop and the data goes stale. Assign someone to maintain it during the migration window and schedule short reviews after each migration wave.
Example inventory: a practical inventory table
A migration inventory can be a spreadsheet with key columns: system name, data type, data residency requirement, current region, target region, owner, and dependencies. Mark which systems touch personal data, which rely on third party services, and which have contractual region requirements. This makes it obvious where legal review is needed. During the inventory, teams often discover hidden dependencies like US based analytics tools or backup storage in another region. Catching those early prevents compliance surprises.
Pitfalls in the inventory phase
- Ignoring SaaS tools that export data outside the EU.
- Forgetting disaster recovery regions and backup policies.
- Assuming data residency is covered by encryption alone.
- Missing integration points like batch exports and BI tools.
- Not involving legal or privacy teams until late.
Inventory checklist
- Identify every system and the data it stores or processes.
- Record data residency requirements and contract obligations.
- Map dependencies, including SaaS and data export paths.
- Confirm backup, DR, and logging locations.
- Validate encryption, access control, and audit logging.
- Review findings with legal and security teams.
Data classification rubric: A consistent classification rubric reduces debate. Define categories such as personal data, operational telemetry, financial records, and anonymized analytics. For each category, specify the allowed regions and retention period. This helps teams make fast decisions during the inventory without waiting for legal to review every system.
Use the rubric in your inventory template so every system is classified the same way. Migration sequencing: Sequence migrations by risk. Start with low risk systems that have no personal data and few dependencies. Use those early moves to validate network connectivity, identity, and logging in the EU region. Then migrate more complex systems in waves. This reduces risk and creates momentum.
