They can be very very very nice if you have a lengthy (or perhaps just unpredictable) build/deploy process. And/or if you have lots of teams working independently on the same monolith.
Suppose you have daily production builds. You are rolling out Feature XYZ. You would like to enable it in prod, but you would like to monitor it closely and may need to turn it off again. Feature flags allow that.
Ultimately what's being achieved is a decoupling of configuration and deployment.
Maybe I'm ranting about "misuse of feature flags", but
I don't like to pontificate about how things ought to be,
but how in my experience they actually are.
Similarly, I might just be making excuses for bad build/deploy processes. =)
At my last job we relied heavily on feature flags via Launch Darkly. I will admit: it was somewhat of a band-aid for the fact that our build process was way too slow and flaky, and that we had too many teams working on an overstuffed monolith.
I also use feature flags when I'm 100% sure stakeholders or PMs will somehow find fault a certain feature after it's deployed, even though they're the ones who specified it, approved it and tested it in a staging environment.
Not exactly the thing that we should be using Feature Flags for, but it saved my ass several times.
On the other hand: this removes some of the accountability that non-technical folks have over software. This can be detrimental in the long term.
I have also found that for UIs the best thing to do is have a staged rollout approach.
Internals / Friendly users / Less friendly users / VIPs.
The blast radius & intensity of explosion is smaller on the earlier groups.
The groups themselves need not be fixed. If you have a stakeholder/group that demanded the new features, they can be in an early wave. Inevitably they may be the ones to find defects in it, so the sooner the better.
Suppose you have daily production builds. You are rolling out Feature XYZ. You would like to enable it in prod, but you would like to monitor it closely and may need to turn it off again. Feature flags allow that.
Ultimately what's being achieved is a decoupling of configuration and deployment.
Similarly, I might just be making excuses for bad build/deploy processes. =)At my last job we relied heavily on feature flags via Launch Darkly. I will admit: it was somewhat of a band-aid for the fact that our build process was way too slow and flaky, and that we had too many teams working on an overstuffed monolith.