A developer should choose a back-end web development language based on several factors, including:

1. Project requirements: The specific requirements of the project, such as scalability, performance, security, and functionalities, will play a key role in determining the best language.
2. Developer skills and expertise: The developer should choose a language that they are familiar with or are eager to learn, as this will impact their ability to deliver a high-quality project in a timely manner.
3. Community and resources: A robust community of developers and resources, such as tutorials, forums, and libraries, can make it easier for the developer to find support and solutions to problems.
4. Popularity and demand: Choosing a popular and in-demand language can make it easier for the developer to find job opportunities and build a career in the field.
5. Performance and scalability: Some languages are better suited to large-scale, high-traffic projects, while others are better suited to small, lightweight applications.
6. Cost: Some languages may be more expensive to use or require more powerful hardware, which should be taken into consideration when making a decision.

Ultimately, the best language for a particular project will depend on a combination of these factors, as well as the personal preferences of the developer. The developer should carefully consider all of these factors before making a final decision.