Definition
Data Residency refers to configuring data storage locations by region to ensure that data is stored in the specific country/region required by the customer or regulations. It works in conjunction with Data Localization, Multi-Region deployment to meet the requirements of GDPR, data cross-border compliance, and enterprise customers' data sovereignty requirements.
Compliance Background
The EU GDPR requires that cross-border transfers of personal data comply with adequacy decisions, SCC standard contractual clauses, or BCR and other mechanisms; countries like China, Russia, and India require certain data to be stored domestically; enterprise customers (especially in finance, healthcare, and government) often require data to be stored in specified regions. Data Residency is the foundational capability for platforms to meet these requirements and must be implemented in architecture design, deployment, and operational processes.
Technical Implementation
Achieving Data Residency requires: deploying data centers in target regions or using local clouds; storing data partitioned by customer and business to avoid mixed storage across regions; isolating sensitive data such as CDR, usage, billing, and user information by region; ensuring backups, disaster recovery, and log storage comply with residency requirements; cross-border transfers must go through compliance mechanisms such as DPA and SCC. The platform must provide a configuration interface allowing customers to select data storage regions.
Practice in ICMP
SimtoLink ICMP supports Multi-Region deployment and can configure Data Residency according to customer needs: EU customer data is stored in the EU region; Asia-Pacific customers can choose Singapore, Hong Kong, etc.; supports Data Localization enforced local scenarios. The platform Audit Trail records data storage and access to meet compliance audits.
A residency policy names the primary storage region
Data residency is the agreement on which geographic region a customer’s primary data is written to. Once that primary region is set, account details, SIM and usage detail tied to that customer, and invoice working papers should be created there. It is a placement decision in the architecture, used to meet contract and regulatory requirements about where data sits. Placement and access speed are not the same goal. An entry point can sit at the edge so reads are nearby, but the authoritative copy should stay in the agreed region.
Residency has to land on concrete data classes, not on the sentence “everything is in the cloud.” Configuration, public documents, and customer personal data can live in different regions. Without a classification, operators create every new table in the default region. The default is often the first region the platform opened, which is not necessarily the region agreed with the customer. The region identifier should be written in the tenant configuration and read by the service that creates the data. It cannot live only in an appendix to the sales contract.
When the region a customer may choose and the legal region differ
When a customer wants a region that is faster to reach, but the industry or the data type must stay in another region, the stricter rule wins. The list of choices should not include a region the regulation excludes. A tenant that was already placed wrongly needs a migration path: stop writes, copy to the target region, check record counts and checksums, switch reads and writes, then delete the copy in the source region. Changing only the configuration, and not moving the data, puts new records in the new region while old records stay in the old one.
If a cross-border transfer is still necessary, for example handing a summary to a settlement service in another region, use the mechanism named in the contract and limit the fields. Where data localization also applies, the localization list takes priority over customer preference. The place support staff sit is not the storage region. A remote view is still an access, and it should be written to the audit trail. The processor’s office being inside the agreed region does not make a backup stored somewhere else the same residency.
Disaster-recovery replication that takes data outside the agreed region
High-availability designs often place a copy in another region. If that region is outside what the customer agreed, disaster-recovery replication changes residency. Sound disaster recovery first looks for a second availability zone or a second site inside the same residency boundary. A copy goes outside the region only when the contract explicitly allows cross-region disaster recovery, and the contract states where data will land on failover. Turning on cross-region replication without that statement means the day of failover is when you discover the data has already left the country.
Test environments are another exit. Filling a foreign test database with production detail records breaks residency in the same way. Analytics jobs, search clusters, and “replicate to an archive region” in an object-storage lifecycle rule all need their target location checked. After a failover drill, confirm that temporary copies were deleted, not only that traffic was switched back to the primary region. A change to the region configuration itself should keep the value before and the value after. When a customer asks where the data is, the answer should come from the actual storage location, not from the region name on the cover of the contract. If the two disagree, stop widening replication first, then plan the move back.
Choosing the region when the tenant is created is much cheaper than migrating later. Options in the creation wizard should come from the region list that customer is allowed to use, not from every region the platform has. If a tenant that already has data must change, first stop jobs that write personal data, then copy, check, switch, and delete. Detail records that arrive during the switch window should be staged in the target region. They must not keep writing to the source region that is about to be retired. Support tools should show the region where the data actually sits. Showing the region name from the contract while connecting to another database leaves the residency promise only in the interface copy.