Regions and availability zones
🏠The everyday picture
A bank with branches in several cities, and within each city, branches in different areas. If one area floods, the other branches keep working; if a whole city has a crisis, other cities carry on.
📘What it really is
- A region is a geographic area with cloud data centres: Mumbai, Hyderabad, Delhi, Singapore, Frankfurt.
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Each region has several availability zones (AZs): separate data centres with independent power, cooling and networking, close enough for fast connections between them.
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Choosing a region:
- near your users for speed (Indian regions for Indian users);
- data residency: laws or contracts may require data to stay in India;
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services and prices differ between regions.
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High availability within a region: run copies of your app in two or more zones behind a load balancer; use a managed database with a standby replica in another zone that takes over automatically if the main one fails.
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Disaster recovery across regions: keep backups (and perhaps a standby) in a second region, for the rare case of a whole-region outage.
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More availability costs more. Decide from your availability needs (Module 67) and RPO/RTO targets (Module 58).
🖱️Try it
Find which regions your chosen provider has in or near India, and how many zones each has. Write your CRM's availability plan: how many zones for the app, whether the database has a standby, where backups are copied, and the expected RPO and RTO.
✅Quick check
What's the difference between a region and an availability zone?
Show the answer
A region is a geographic area; availability zones are separate data centres within it.
How does running in two zones help?
Show the answer
If one data centre fails, the other keeps serving traffic.