Geo-Sharding & Data Residency
You'll learn to
- -Explain why regulations like GDPR affect data placement
Data Residency Requirements
GDPR in Europe and similar regulations elsewhere impose a constraint that has nothing to do with performance: certain user data must physically stay within specific geographic or legal boundaries, full stop. This turns "where does this data live" from a purely technical decision into a compliance requirement.
Geo-Sharding
Instead of (or in addition to) sharding by hash or key range, as the earlier Sharding chapter described, geo-sharding partitions data by the user's region. A European user's data lives on European infrastructure and simply never replicates outside it, satisfying the legal requirement, but at the cost of new edge cases: what happens when that user travels to another continent, or when an internal analytics query needs to aggregate a metric across every region at once?
A user's data is pinned to their home region's shard by law, not by load; it never replicates to another region's database at all.
These edge cases turn geo-sharding from a storage detail into an architectural one: it touches request routing, caching policy, and even how you design your APIs, not just where a database file happens to sit.
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