Taking over requires authority, state, and routing#
A primary becomes unreachable. Detection is uncertain: slow can look dead. Promotion must establish which replica has authority, assess replication lag, redirect clients, and prevent the old primary from writing if it returns.
Use these prompts to extend the design. The useful answer is a reasoned change, not a memorized sentence.
- Was the replica caught up?
- Who is authorized to promote it?
- Can the surviving capacity carry all traffic?
- How is failback validated?
Related practice problems
Use the manifest-backed prompts below to apply this lesson in a complete design.
- Reliability design patternsMicrosoft Azure Architecture Center
Reach this point to mark the lesson as read.