RDB configuration (save intervals) in Redis - Step-by-Step Execution

Concept Flow - RDB configuration (save intervals)

Start Redis Server

↓

Check save intervals config

↓

Monitor changes in data

↓

Has changed keys count reached threshold?

↓

Wait and keep monitoring

↓

Save snapshot to disk

↓

Reset change counter

↓

Continue monitoring

Redis monitors data changes and triggers saving snapshots to disk when configured thresholds of time and changes are met.

Execution Sample

Redis

save 900 1
save 300 10
save 60 10000

This config saves the database if 1 change in 900 seconds, or 10 changes in 300 seconds, or 10000 changes in 60 seconds occur.

Execution Table

Step	Elapsed Time (sec)	Changes Count	Condition Checked	Action Taken
1	0	0	No save condition met	Continue monitoring
2	300	5	save 300 10? 5<10	Continue monitoring
3	600	10	save 300 10? 10>=10	Trigger RDB snapshot
4	600	0	Reset changes count after save	Continue monitoring
5	900	1	save 900 1? 1>=1	Trigger RDB snapshot
6	900	0	Reset changes count after save	Continue monitoring
7	1200	9999	save 60 10000? 9999<10000	Continue monitoring
8	1260	10000	save 60 10000? 10000>=10000	Trigger RDB snapshot
9	1260	0	Reset changes count after save	Continue monitoring

💡 Monitoring continues indefinitely, snapshots triggered when conditions meet.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 5	After Step 7	After Step 8	Final
Elapsed Time (sec)	0	300	600	900	1200	1260	1260
Changes Count	0	5	0	0	9999	0	0

Key Moments - 2 Insights

Why does Redis reset the changes count after saving a snapshot?

After saving a snapshot (see steps 3, 5, 8), Redis resets the changes count to zero to start counting new changes for the next save interval.

What happens if changes do not reach the threshold within the time interval?

Redis continues monitoring without saving (see step 2 and 7), because the condition for saving is not met yet.

Visual Quiz - 3 Questions

Look at the execution table, at which step does Redis first trigger a snapshot save?

A Step 3

B Step 5

C Step 2

D Step 7

💡 Hint

Check the 'Action Taken' column for the first 'Trigger RDB snapshot' entry.

According to the variable tracker, what is the changes count after step 3?

A 10

B 0

C 5

D 1

💡 Hint

Look at the 'Changes Count' row under 'After Step 3' in the variable tracker.

If the changes count never reaches the threshold, what will Redis do?

A Save snapshot anyway after time interval

B Never save snapshot

C Continue monitoring without saving

D Reset changes count to zero

💡 Hint

Refer to steps 2 and 7 in the execution table where conditions are not met and monitoring continues.

Concept Snapshot

RDB save intervals config:
- Format: save <seconds> <changes>
- Redis saves snapshot if changes >= threshold within seconds
- Multiple save rules can coexist
- After saving, changes count resets
- Monitoring continues indefinitely

Full Transcript

Redis RDB configuration uses save intervals defined by time and number of changes. Redis monitors data changes and elapsed time. When the number of changes reaches or exceeds the configured threshold within the specified time, Redis triggers a snapshot save to disk. After saving, the changes count resets to zero to start fresh counting. If the threshold is not met, Redis continues monitoring without saving. Multiple save intervals can be configured to trigger saves under different conditions.