What is Data residency?
The legal/regulatory requirement that customer data physically reside in a specific jurisdiction. Driven by GDPR (EU), data-protection laws in Switzerland, Australia, India, China, Saudi Arabia, etc. Increasingly material for SaaS targeting non-US customers.
Full explanation
Data residency requirements force SaaS providers to provision separate infrastructure per jurisdiction. EU data must remain in EU regions (post-Schrems II this is enforced strictly); some sectors (German finance, French healthcare, Swiss banking) require data to remain in country, not just region. The architectural impact: separate database clusters, separate object storage, separate inference endpoints, separate logging pipelines per residency region. For startups, the practical answer is to add residency tiers as customers require — most US-only SaaS does not need EU residency until the first EU enterprise customer signs.
Example
A SaaS targeting EU enterprise customers cannot route Stripe customer-data through US Stripe Atlas if the customer's data-processing-agreement requires EU residency. The fix: provision a Stripe instance in EU + a Supabase project in eu-west-1 + an OpenAI project in EU + ensure Vercel function regions are EU-only. Compliance posture is a contractual obligation, not just a technical one.
Related
FAQ
When does data residency become a real requirement?
Typically the first EU / regulated-jurisdiction enterprise customer who sends a procurement questionnaire. Pre-that, the technical answer is 'we are US-hosted' and most early-stage prospects accept it. Post-that, you have a real engineering project to provision residency-compliant infrastructure.
Does Vercel / Supabase support data residency?
Both have region-pinning. Vercel functions can be pinned to specific regions; Supabase projects are created in a chosen region (eu-west-1, ap-southeast-1, etc.). The architectural work is making sure the rest of your stack (third-party APIs, logging, observability, inference providers) honors the same residency.