MapReduce. Leveraging lower level abstractions incipient in the early Google datacenter (distributed FS, distributed process executor) and providing a simple but expressive programming model for distributed large scale batch computations. A significant amount of effort went into documenting and exemplifying the usage of the programming model for a large number of use-cases. Chosen to serve thousands of use-cases all across a fast growing company. Developed by 2 people. A fantastic example of '10[00]x engineering', and yet I can't imagine something more antithetic to the 'lone gunman' strawman.