Feature flags concept in Spring Boot - Step-by-Step Execution

Concept Flow - Feature flags concept

Start Application

↓

Check Feature Flag Status

↓

Run Code Based on Flag

↓

End

The app starts, checks if a feature flag is ON or OFF, then runs code accordingly.

Execution Sample

Spring Boot

boolean isFeatureEnabled = featureFlagService.isEnabled("newFeature");
if (isFeatureEnabled) {
    // run new feature code
} else {
    // run old feature code
}

This code checks if a feature flag is enabled and runs code based on that.

Execution Table

Step	Action	Feature Flag Checked	Flag Value	Code Path Taken
1	Start application	N/A	N/A	N/A
2	Check feature flag 'newFeature'	newFeature	true	Run new feature code
3	Execute new feature code	newFeature	true	New feature code runs
4	End execution	N/A	N/A	N/A

💡 Feature flag 'newFeature' is true, so new feature code runs and execution ends.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
isFeatureEnabled	undefined	true	true	true

Key Moments - 2 Insights

Why does the code run the new feature instead of the old one?

Because the feature flag 'newFeature' is true at step 2 in the execution_table, so the if condition is true and new feature code runs.

What happens if the feature flag is false?

If the flag was false, the else branch would run old feature code instead, as shown by the decision in step 2.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'isFeatureEnabled' after step 2?

A true

B false

C undefined

D null

💡 Hint

Check the variable_tracker row for 'isFeatureEnabled' after step 2.

At which step does the application decide which code path to run?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Code Path Taken' column in execution_table for when the decision happens.

If the feature flag was OFF, how would the 'Code Path Taken' change at step 2?

A No code runs

B Run new feature code

C Run old feature code

D Application crashes

💡 Hint

Refer to the concept_flow where OFF leads to disabling the feature and running old code.

Concept Snapshot

Feature flags let you turn features ON or OFF without changing code.
Check flag status in code, then run new or old feature accordingly.
In Spring Boot, use a service to get flag value.
This helps test or release features safely.
Always check flag before running feature code.

Full Transcript

Feature flags are like switches in your app. When the app starts, it checks if a feature flag is ON or OFF. If ON, it runs the new feature code. If OFF, it runs the old code. This lets developers control features without changing the app code every time. In Spring Boot, you might call a service to check if a feature is enabled. Then, use an if statement to decide which code to run. This way, you can test new features safely or turn them off if needed.