Reel · Terraform & Infra · Oct 28, 2026
Ek tapri band… aur poora app band? Region, AZ and failover over chai
In short
Tech Tapri, Ep 1: cloud words over chai. A Region is the whole area (think Connaught Place). An Availability Zone is a separate tapri in that area, with its own cylinder and its own doodhwala. Failover is when Sharma ji's cylinder runs out and you walk two steps to Gupta ji's tapri. Warm standby means the milk there is already hot. In Oct 2025, a DNS problem in AWS us-east-1 shook a big part of the internet for hours. Having a backup isn't enough; sometimes you have to close a tapri yourself and test.
Checklist: what to do about it
- Write down which Region and which AZs your app actually runs in.
- Check that each AZ can carry the load if another one goes dark.
- Decide what your standby is: cold, warm or active. Know how long each takes to serve traffic.
- Find the single things every AZ shares (a database primary, a DNS record, a config service).
- Take one AZ away on purpose, in staging, and time the failover.
- Write the failover runbook as one page, and store it somewhere that survives the outage.