* Produce field-level mapping between different schemas, including transformation rules, default values, and handling for fields with no equivalent.
* Define data quality and reconciliation rules — what "good" looks like post-migration, what tolerance is acceptable, and how exceptions are handled.
* Define the initial bulk migration approach (one-shot vs phased, by member cohort, by data domain), volumes, and cutover criteria.
* Define historical data scope — how far back history must be migrated for regulatory, user-experience and actuarial reasons.
* Specify cross-cloud integration model
* Identify every integration point
* Specify the integration pattern per flow (synchronous API, event/stream, batch), latency and throughput requirements, and failure/retry expectations.
* Capture cross-cloud concerns: egress, network topology, authentication/identity federation between AWS and GCP, and any data residency constraints that affect where data can land.
* The above needs to take into account the impact to the current Data Warehousing estate and establish a ‘lowest impact’ approach so that teams using these services will have only the required minimum disruption
* Business process and member-journey mapping
* Map the current journeys and overlay them onto the target equivalents to show where user experience changes, breaks, or needs reconciliation.
* Identify business rules that differ between source and target and flag decisions the business needs to make about which rule set wins.
* Non-functional and regulatory requirements
* UK-specific regulatory requirements (UK GDPR, FCA where insurance touchpoints are involved, data residency, consent and right-to-erasure handling) and how they translate onto a GCP-hosted platform.
* Performance, availability, and SLA expectations the UK business currently relies on
* Security, audit and observability requirements carried over from the UK platform.
* Stakeholder map and decision log
* Identify decision-makers and SMEs across different teams and establish a working cadence with each.
* Maintain a decision log capturing every "which platform's rule wins" or "do we migrate this or sunset it" call, with rationale, owner and date — this becomes the single source of truth during execution.
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