Geo Replication & Multi-Region

Core tension

Geo improves latency + availability, but increases consistency-routing complexity.

Planner responsibilities

• choose healthy regions
• satisfy R/W by replica count
• minimize latency
• report quorum safety

Routing rule

Sort healthy regions by latency (then name). Accumulate replicas until quorum reached.

Route latency = slowest selected region latency.

Safety rule

With healthy replica total N:

• R + W > N
• W > N/2

Feasible route can still be unsafe.

Build

Geo quorum planner that outputs:

• read/write region paths
• read/write latencies
• intersection safety flag