hardMultiple Choice
Database Backup Strategy for Recovery Time and Point Objectives
A large enterprise is implementing a backup strategy for a critical database that requires an RTO of 2 hours and an RPO of 15 minutes. The database is 2 TB in size. Which backup method would BEST meet these requirements while minimizing storage costs?
Quick Answer
The correct answer is weekly full backups with transactional log backups every 15 minutes. This method meets the 15-minute RPO by capturing every database change in the transaction log at that exact interval, while the weekly full backup provides a clean restore base; together, they allow recovery to any point within 15 minutes without the storage overhead of daily full backups. On the CISA exam, this question tests your understanding of balancing RTO and RPO with storage efficiency—a common trap is choosing daily full backups, which waste storage and fail to meet a tight RPO, or assuming log backups alone suffice without a full backup foundation. Remember the mnemonic: “Full for foundation, logs for loss”—the full backup anchors the restore, and frequent logs keep data loss under 15 minutes.
⚠ Common exam trap
CISA often tests the distinction between RPO and RTO and the cost implications of backup methods, so candidates who focus only on RPO pick CDP or frequent fulls without considering storage cost or RTO.
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
✓
Weekly full backups with transactional log backups every 15 minutes
Weekly full backups with transactional log backups every 15 minutes meets the RPO of 15 minutes because logs capture all transactions since the last log backup, and meets the RTO of 2 hours because restoring the full backup plus applying log backups can be completed within that window. It minimizes storage costs compared to daily fulls or CDP because full backups are infrequent and logs are small and incremental.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Daily full backups
Why it's wrong here
Daily full backups leave up to 24 hours of data loss, breaching the 15-minute RPO, and copying 2 TB daily inflates storage. Full backups are tempting for their simple restore, which would satisfy the 2-hour RTO, but the RPO requirement rules them out here.
- ✗
Continuous data protection (CDP) replicating to a remote site
Why it's wrong here
CDP replicating to a remote site meets the 15-minute RPO and 2-hour RTO, but continuous replication of every write to a second site consumes substantial storage and bandwidth, contradicting the cost-minimisation requirement. CDP suits near-zero RPO scenarios where storage cost is secondary, not this cost-sensitive brief.
- ✓
Weekly full backups with transactional log backups every 15 minutes
Why this is correct
Transaction log backups every 15 minutes satisfy the 15-minute RPO, while weekly fulls plus log replay meet the 2-hour RTO. This combination minimises storage costs compared with frequent full or differential backups of a 2 TB database.
- ✗
A daily full backup and a differential backup every 4 hours
Why it's wrong here
Differential backups every 4 hours give an RPO of up to 4 hours, exceeding the 15-minute requirement, and each differential grows until the next full backup, raising storage. This schedule is tempting as a balanced compromise, but it cannot meet the stated RPO.
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Same concept, more angles
2 more ways this is tested on CISA
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is designing its backup strategy for a critical database that must be available 24/7. The database experiences high transaction volumes. Which backup method minimizes data loss while allowing continuous operations?
easy- A.Offline full backup performed weekly
- B.Differential backup performed daily
- ✓ C.Online backup with transaction log backups
- D.Full backup performed during low-usage periods
Why C: Online backup with transaction log backups (Option C) is correct because it allows the database to remain fully operational (24/7 availability) while capturing every committed transaction in the transaction log. In the event of a failure, you can restore the most recent full backup and then apply all subsequent transaction log backups to recover to the exact point of failure, minimizing data loss to only uncommitted transactions.
Variation 2. An organization is implementing a backup strategy for its critical database. The database is updated continuously during business hours, and the recovery point objective (RPO) is 15 minutes. Which backup method should be used to meet the RPO while minimizing backup storage and performance impact?
medium- A.Perform full backups every 24 hours
- B.Implement synchronous replication to a standby server
- ✓ C.Perform incremental backups with transaction log backups every 15 minutes
- D.Perform differential backups every 6 hours
Why C: Incremental backups with transaction log backups every 15 minutes meets the 15-minute RPO by capturing all changes since the last full or incremental backup, while transaction log backups record every individual database transaction. This method minimizes storage by only backing up changes and reduces performance impact compared to continuous replication, as log backups are lightweight and can be scheduled without constant I/O overhead.
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISACA exam blueprint
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