Differences in the production environment

It is often the case that the code produced by developers works fine in a development environment, but not in production. A lot of the time, this is because the production environment is very different from other environments, and some unforeseen errors occur. The common mistakes involve the development environment, because services are collocated on the same servers, or there isn't the same level of security. As a consequence, services can communicate with one another in development, but not in production. Another issue is that the development environment might not run the same versions of a certain library/software, and therefore, the interface to communicate with them might differ. The development environment may be running a newer version of a service, which has new features that the production doesn't have yet; or it could be simply a question of scale. Perhaps the dataset used in development isn't as big as that of production, and scaling issues will crop up once the new code is out in production.