Warm Standby vs Pilot Light: Choosing the Right DR Strategy
A payments platform requires disaster recovery across Regions. Requirements: RPO of 15 minutes and RTO of about 1 hour. The business cannot afford full duplicate capacity in both Regions all the time, but the team wants automated readiness so failover is mostly operationally guided rather than a slow rebuild. Which DR strategy is the best fit?
⚠ Common exam trap
A common mix-up: candidates confuse pilot light with warm standby, assuming minimal infrastructure is sufficient for a 1-hour RTO, but pilot light requires provisioning compute resources after failover, which adds significant time, whereas warm standby already has compute running and only needs scaling.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Warm standby, keeping core infrastructure and a partially provisioned environment ready in the secondary Region with frequent data replication.
Warm standby is the best fit because it maintains a partially provisioned environment in the secondary Region with core infrastructure (e.g., a smaller EC2 instance fleet, a replicated database) and uses frequent data replication (e.g., Amazon RDS cross-Region replication or DynamoDB global tables) to achieve an RPO of 15 minutes. The RTO of about 1 hour is achievable by scaling up the standby environment and redirecting traffic, which is faster than a full rebuild but avoids the cost of full duplicate capacity. This balances the business constraint of not affording active/active with the need for automated readiness and guided failover.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Backup and restore only, relying on scheduled snapshots and manual restores during incidents.
Why it's wrong here
Scheduled snapshots cannot meet a 15-minute RPO, and manual restores exceed the one-hour RTO. Backup and restore suits non-critical workloads tolerating hours of data loss and lengthy rebuilds; here the RPO and RTO demand continuous replication with automated recovery.
- ✗
Pilot light, keeping only minimal infrastructure in the secondary Region and starting full services after failover.
Why it's wrong here
Pilot light keeps only a minimal core running, so the full application tier must still be provisioned and started during failover, which cannot reliably meet a one-hour RTO. It suits cost-sensitive DR where RTO tolerates hours of rebuild; warm standby, with scaled-down but running services, fits this scenario.
- ✓
Warm standby, keeping core infrastructure and a partially provisioned environment ready in the secondary Region with frequent data replication.
Why this is correct
Warm standby keeps core services and a scaled-down but functional environment running in the secondary Region with continuous replication, achieving the 15-minute RPO and roughly one-hour RTO. It avoids the cost of full duplicate capacity while remaining far faster than a rebuild.
- ✗
Active/active, routing production traffic to both Regions continuously and accepting dual-region complexity.
Why it's wrong here
Active/active runs full duplicate capacity in both Regions continuously, contradicting the stated budget constraint. It fits workloads needing near-zero RPO and RTO where dual-region cost is justified; here warm standby provides the required replication and automated readiness without permanent duplication.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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