Goldilocks was the lead of a software development team. She needed to review pull requests from three of her team members.

The first developer's code was a mess. It relied on some deprecated features of an outdated library. The few modules were long and complex, trying to do too many different things. There were no tests, so it was impossible to be sure the code was bug-free. The architecture needed to run on a single server, so it could never scale up. There was no way to know whether it did what it was supposed to do.

The second developer's code was also a mess. The system was built using some brand new libraries and coding paradigms. The system comprised of a dozen different interconnected microservices. There was a very thorough test suite, testing every implementation detail. The system included infrastructure as code, but couldn't run on a single computer. There was no way to know whether it did what it was supposed to do.

The third developer's code was just right. It used the latest versions of libraries the team was familiar with. The system was split up into a dozen simple modules. It was obvious what each module did, and how it fit within the business requirements. There were a few tests for the core functionality, so she knew that it was working. The system was easy to get running, but was simple enough to scale up infinitely. It was very easy to understand, and to know that it did what it was supposed to do.

Goldilocks then had a meeting with the three developers.

She told the first developer their code was under-engineered. She said they should take some time to simplify it and make it easier for other developers to understand and work with it.

She told the second developer their code was over-engineered. She said they should take some time to simplify it and make it easier for other developers to understand and work with it.

She said well done to the third developer and approved the pull request.