Cloud Infrastructure · Cluster
Multi-Region Design
Failover, data residency, and latency.
- 01 The Inter-Region Latency Floor Set by Fiber Paths Why the minimum round-trip time between two regions is fixed by geography and glass rather than by provisioning, and how to compute that floor before choosing a topology.
- 02 Decomposing the Failover Time Budget How detection delay, decision quorum, promotion, and traffic redirection add up into a recovery time, and which of the four terms an operator can actually shorten.
- 03 DNS Failover and the Resolver Caching Bound How record TTLs, negative caching, and resolver behaviour put a floor under DNS-based traffic redirection, and why the observed switchover time exceeds the TTL.
- 04 Replication Lag as the Real Recovery Point Bound Why asynchronous cross-region replication sets an RPO that varies with write rate and network conditions, and how to measure the lag that actually matters for data loss.
- 05 Conflict Resolution When Two Regions Accept Writes Last-writer-wins, version vectors, and application merge: what each guarantees about concurrent cross-region updates, and which invariants each one breaks.
- 06 Quorum Placement and the Latency of the Second-Fastest Replica How the geometry of replica placement decides commit latency for majority quorums, and why adding a distant replica to a three-node group can be free or fatal.
- 07 Pinning Data to a Region Without Freezing the Control Plane How residency constraints translate into placement rules, which metadata still leaks across borders, and why the control plane and data plane need different regionality.
- 08 Fencing Tokens and the Arithmetic of Lease Expiry Why a promoted primary must wait out the old primary lease before accepting writes, how fencing tokens stop a stalled writer, and where the wait comes from.
- 09 Cell-Based Isolation and the Blast Radius of a Bad Deployment How partitioning a regional deployment into independent cells limits the reach of a failure, what the cell map costs, and why cells differ from availability zones.
- 10 Sizing Regional Capacity for the Loss of a Region Why N+1 regional capacity is larger than the arithmetic suggests, how queueing turns the last few percent of utilization into latency, and where failover load comes from.