I'm going to tell you a little bit how we work on features at GitHub. It's simple, but very powerful in my opinion. At GitHub we have a high performance culture.

We are deploying changes almost all the time while keeping the service running and the deployment failure ratio needs to be super low! We are constantly working on new medium/big features, we have frequent deploys and required peer reviews.

How do we know that big features are not conflicting with each other in functionality and in version control. How do we merge the work done in these non-trivial features? How do we do prevent peer reviews slow down our productivity?

With basically two things: split the work in small batches and feature flags. We don't have long-lived feature branches. We do very small changes all the time and deploy them.

We could split a feature in tens or hundreds of PRs, but until it is beta or GA, we don't expose it to users by using feature flags.