GDPR, DPDP, and other laws mandate data stays in region. Geo-partitioning by region satisfies compliance AND puts data close to users.
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The mechanic
User's registered region determines shard. All their data in that region. Cross-region reads rare + expensive.
The mechanic
User's registered region determines shard. All their data in that region. Cross-region reads rare + expensive.
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Data residency
GDPR: EU data in EU. DPDP: Indian citizen data in India. Regulators check.
Latency wins
User in Mumbai queries Mumbai shard. 10ms vs 150ms across ocean. Better UX.
Cross-region features
Some features need global view (search all listings). Federate queries or maintain global replica of hot data.
Migration complexity
User moves EU→US? Move their data or fork it? Legal nightmare. Design carefully.
Region-per-user shard. Regulatory + latency compliance. Cross-region features are the hard part.