In large companies, a culture of A/B testing every decision can become a crutch that stifles innovation and speed. It leads to risk aversion and organizational lethargy, as teams lose the muscle for making convicted, gut-based decisions informed by qualitative customer feedback.

The now-ubiquitous "hold to pause" feature in Stories was created because engineer Ryan Peterman felt it should exist while dogfooding the product. He instinctively tried to pause a video with his thumb, and when it didn't work, he simply built it. This shows how engineers can drive product innovation by implementing their own user instincts.

Near the launch of Instagram Stories, the team was in a bind after losing their drawing tools engineer. Co-founder and CTO Mike Krieger exemplified a "lead from the front" mentality by personally jumping in to code the remaining features, like the neon brush, and review diffs at 2 AM. This hands-on leadership from the top inspired the team.

Adopt an "unshipping" culture. If a feature doesn't meet a predefined usage bar after launch, delete it. While a small subset of users may be upset, removing the feature reduces clutter and confusion for the majority, leading to a better overall user experience.

Major tech successes often emerge from iterating on an initial concept. Twitter evolved from the podcasting app Odeo, and Instagram from the check-in app Burbn. This shows that the act of building is a discovery process for the winning idea, which is rarely the first one.

As a junior IC at Instagram, Adrian was told leadership had "bigger fish to fry" than his A/B testing idea. He built a scrappy, functional prototype anyway, recruiting a PM for air cover. This bottoms-up initiative proved its value and ultimately led to his first senior promotion.

Instead of only testing minor changes on a finished product, like button color, use A/B testing early in the development process. This allows you to validate broad behavioral science principles, such as social proof, for your specific challenge before committing to a full build.

When the Instagram Stories project was churning, leadership made a counterintuitive move: they significantly cut the team size. This resulted in clearer ownership, less communication overhead, and faster decision-making, allowing a tiny core team to build and ship the massive feature in just a few months.

Contrary to the classic engineering rule to "never rewrite," Block's CTO believes AI will make this the new standard. He is pushing his teams to imagine a world where for every release, they delete the entire app (`rm -rf`) and rebuild it from scratch, with AI respecting all incremental improvements from the previous version.