Glossary term
What is Active-active / Active-passive? Meaning for developers
Both copies serve traffic / one waits as backup. Example: Two regions serving users vs a standby region.
Learn it properly · System DesignLesson 40: Single Points of Failure, Redundancy & FailoverThe site went down, and the culprit was none of the redundant boxes on the diagram but the one NAT gateway, the one DNS provider, or an expired certificate. How to hunt single points of failure, shrink blast radius, add redundancy that works, and fail over without split brain.