What is meant by hardcoding data in code and why can it be problematic?

Hardcoding data — this is when values such as strings, numbers, file paths, URLs, or configurations are directly embedded in the source code instead of being stored in external configuration files or retrieved from parameters.

Problems of hardcoding:

• Difficulty of change: to change a value, you need to edit the code and rebuild the application.
• Lack of flexibility: it is not easy to adapt the application to different environments (for example, testing and production).
• Security: if secrets (passwords, keys) are stored in the code, there is a risk of leakage.
• Testing: it is more difficult to substitute data for tests.

Therefore, it is recommended to move such data to configuration files, environment variables, or use special services for managing settings.