A cold pail of water passes through a line of workers, sloshing from hand to hand. Another follows behind it. And another. To coordinate this bucket brigade, the line of busy hands moves according to a fixed rhythm, each movement synchronized like a metronome.
The analogy illustrates the primary principle of synchronous processing: no matter the speed of a single movement, the pace of the chain may not exceed the time it takes the slowest transfer to complete. This familiar scene is the basic unit of Fordismβan assembly line of exchanges locked in linear progression. One thing at a time. One thing after another. All you can really do is speed it up. This dictatorship of synchronyβfrom clocked computer chips to supply chains and back againβhamstrings productivity and constrains the marketplace.
For the designers of scalable systems, it represents the ultimate barrier to progress. To break through this barrier, engineers dream of the asynchronous : a vision of the world where the bucket brigade stops following the tick of the metronome.
In the event that one worker finishes passing their bucket early, they can accept the next from anywhere along the line. Instead of waiting for the second worker to pass their bucket, the third takes it directly from the first, or from a different line entirely.
Work flows to available resources, regardless of where these resources are located in the traditional sequence. At first, the line becomes chaotic. But suddenly, the light accelerates past the heavy.
