You've probably heard of Amazon's two-pizza-team rule: No team should be larger than the number of people that can be adequately fed by two large pizzas. 

What you likely don't know is that despite the approach's initial success, few people inside Amazon actually talk about two-pizza teams.

Instead, the model was gradually refined and ultimately replaced by a far more capable type of team model, one still in use today.

As Colin Bryar and Bill Carr describe them in their fascinating new book Working Backwards: Insights, Stories, and Secrets from Inside Amazon, two-pizza teams were small. Autonomous. Measured by a well-defined set of metrics. Owned responsibility for all aspects of their area of focus: design, technology, business results, etc.

All of which sounds great in theory.

Yet sometimes two pizzas really weren't enough.

Plus, two-pizza teams were only successful for tasks like product development, an area where tangled dependencies had historically slowed the rate of innovation and implementation. It's hard to get something done when another functional area resists, much less actively works against you.

Worst of all, Amazon found that the biggest predictor of a team's success wasn't whether it was small but whether it had a leader with "the appropriate skills, authority, and experience to staff and manage a team whose sole [my italics] focus was to get the job done."

Or as Amazon's SVP of devices, Dave Limp, said, "The best way to fail at inventing something is by making it somebody's part-time job."

That's why, in time, two-pizza teams evolved into single-threaded leader (STL) teams, a term borrowed from computer science that means to only work on one thing at a time.

Fulfillment by Amazon

Single-threaded is term borrowed from computer science that means to only work on one thing at a time.

One example of how a single-threaded leader team succeeded where two-pizza teams failed? The idea that became Fulfillment by Amazon (FBA).

The idea behind FBA was simple: give third-party sellers access to Amazon's warehouse and shipping services.

The benefits for third-party sellers were clear: Merchants would send products to Amazon for Amazon to store, pick, pack, and ship on their behalf, not only eliminating a third-party seller's logistics headaches, but making warehousing costs variable rather than fixed.

Executives in retail and operations teams thought FBA was a great idea, but for well over a year nothing happened. They were all "exceptionally capable people, but they didn't have the bandwidth to manage the myriad details FBA entailed," the authors write.

Then Tom Taylor, a VP at the time, was asked to drop all his other responsibilities and was given full authority to hire and staff a team. Crucially, that team was also given sufficient autonomy to build and roll out their assigned task--without coordinating with or seeking approval from other teams.

In short, one highly skilled person was put in charge -- and not only had the authority to see the project through, but was allowed to focus solely on seeing the project through.

As Bryar and Carr write:

A single-threaded leader can head up a small team, but they can also lead the development of something as large as Amazon Echo or Digital Music.

A single-threaded leader of Amazon Echo and Alexa had the freedom and autonomy to assess the novel product problems that needed to be solved, decide what and how many teams they needed, how the responsibilities should be divided up among the teams, and how big each team should be. 

The result?

Sharper focus. Greater creativity. Faster innovation. Clearer authority and accountability. Increased levels of ownership and engagement among team members.

"While these positive outcomes were possible before the first autonomous single-threaded team was created," Bryar and Carr write, "now they have become the natural and expected consequence of this very Amazonian model for innovation."

Putting the STL Into Action

The next time you put a team together, try the STL approach.

Since your organization is likely smaller than Amazon's you may not be able to completely free up the team's leader.

But you can ensure that he or she has sufficient time to devote to leading the project by temporarily reassigning certain tasks, certain responsibilities, etc.

That way the (semi) single-threaded team leader gets the necessary bandwidth to take on the project, and others in your organization get the opportunity to step in, step up, and further develop and expand their skill-sets.

Win-win.

Then decide how many people should be on the team. If you can keep it two pizzas, fine.

One pizza? Even better. The smaller the team, the more manageable and agile. The more valuable each individual feels. And the more invested they tend to be in the overall outcome.

Just make sure that you focus more on choosing a team leader with the skills and experience to get the job done than on the size of the team.

And that you give that person both the time and the authority to actually get the job done.