what is RPO and RTO ?

 

✅ What is RPO (Recovery Point Objective)?

RPO = How much data loss is acceptable?

It defines how far back in time you must recover your database after a failure.

In other words:

RPO tells you how much data you can afford to lose.
It's measured in time (seconds, minutes, hours).

📌 Database Example

Suppose:

• Your database takes backups every 1 hour
• A failure happens at 3:45 PM
• Last backup was at 3:00 PM

Then:

• You lose 45 minutes of data
• So your RPO = 1 hour

If your business says:

• “We cannot lose more than 5 minutes of data”

Then:

• You must implement near real-time replication, e.g.,
  • PostgreSQL sync replication
  • SQL Server AlwaysOn synchronous commit
  • Oracle Data Guard synchronous
  • MySQL Group Replication

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✅ What is RTO (Recovery Time Objective)?

RTO = How much time is acceptable to restore service?

It defines how quickly your database must be back online after a failure.

In other words:

RTO tells you how long you can afford your database to be down.

📌 Database Example

Suppose:

• Your database fails at 3:45 PM
• You restore from backup + perform recovery
• Everything is back online at 4:30 PM

Then:

• RTO = 45 minutes

If your business says:

• Database must be back within 5 minutes

Then you need:

• Automated failover
• Multi‑AZ synchronous replica
• Warm standby instance already running
• No manual restore

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🎯 Putting Both Together (Database Scenario)

Scenario:

Your production PostgreSQL database crashes at 3:45 PM

• Last WAL archive was at 3:40 PM → RPO = 5 minutes
• Failover to standby completes at 3:47 PM → RTO = 2 minutes

This means:

• You lost 5 minutes of data (acceptable based on RPO)
• System was down for 2 minutes (acceptable based on RTO)

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🧩 Easy Analogy

Term	Meaning (Simple)	Database Interpretation
RPO	How much data you can lose	Gap between last usable data & failure time
RTO	How long you can be down	Time database takes to become operational

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🔥 Real-World DB Examples You Can Use

1. Single‑AZ Database

• Backups every night
• No replication
• RPO = 24 hours (you lose 1 day of data)
• RTO = many hours (need to restore backup)

2. Multi‑AZ Synchronous Replication

• Data committed on both nodes
• Failover is automatic
• RPO ≈ 0 seconds
• RTO = 30–120 seconds

3. Multi‑Region Asynchronous Replication

• Slight replication lag (5–15 seconds)
• RPO = a few seconds
• RTO = a few minutes

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⭐ Summary (Very Simple)

• RPO = How much data can I lose?
• RTO = How long can I be down?

Metric Definition             Target

RTO     Max downtime Near 0 seconds

RPO     Max data loss Near 0 data loss

Both are business-driven, implemented through database architecture.