Do I need feature flags if I already use blue-green deploys?

Not necessarily — but they solve different problems.

Blue-green deploys are for releasing infrastructure/app versions safely

Blue-green lets you switch traffic between two environments:

• Blue = current live version
• Green = new version

It’s great for:

• zero-downtime deploys
• fast rollback
• reducing risk during release

But once you flip traffic, everyone gets the new version.

Feature flags are for controlling behavior inside the app

Feature flags let you turn specific functionality on/off without redeploying.

They’re useful for:

• gradual rollout to a subset of users
• testing with internal users only
• A/B testing
• disabling a buggy feature instantly without reverting code
• shipping incomplete code safely

When blue-green is enough

You may not need feature flags if:

• you deploy small, low-risk changes
• you don’t need gradual exposure
• you’re okay with “all users get it at once”
• you can handle rollback by switching environments

When feature flags add value

Feature flags are still useful even with blue-green if you want:

• progressive delivery within the same deployed version
• runtime control over features
• safer release of risky code paths
• operational kill switches
• experimentation and user targeting

Common pattern: use both

A lot of teams use:

• blue-green deploys for release safety
• feature flags for feature safety and rollout control

Rule of thumb

Ask:

“Do I need to control which version is live, or which features within a live version are enabled?”

• If it’s the first: blue-green may be enough
• If it’s the second: feature flags help a lot

If you want, I can also give you a simple decision matrix for when to use blue-green, canary, feature flags, or all three.