Question 1

What's the difference between failover and disaster recovery (DR)?

Accepted Answer

Failover is the automatic switch to a standby system when the primary fails (often within seconds to minutes). Disaster recovery is the broader plan and tooling to restore services after major events (like a region outage), including backups, data recovery, and rebuilding infrastructure. Failover is often one part of a DR strategy.

Question 2

When should I use failover?

Accepted Answer

Use failover when downtime is costly and you need your service to keep running even if a server, zone, or database instance fails. Common triggers include: customer-facing apps with uptime targets (SLAs), critical databases, payment/checkout flows, and systems that must meet RTO/RPO requirements. If brief downtime is acceptable, simpler backups and manual recovery may be enough.

Question 3

How much does failover cost?

Accepted Answer

Costs depend on what must be kept running in standby. Active-passive setups often pay for duplicate capacity (standby instances, storage, replication) plus health checks and data transfer. Active-active can cost more because both sides handle traffic. Managed options (like multi-AZ databases) bundle replication and automatic failover into higher instance pricing. Key cost drivers: extra compute, cross-zone/region data transfer, replicated storage, load balancers/DNS health checks, and testing/operations time.

Failover

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