Always ensure configuration files, especially JSON files, have unique keys. Duplicate keys can cause unpredictable behavior as the last occurrence of a key will overwrite previous values, potentially leading to runtime errors or inconsistent application behavior. When adding new configuration: - Check for existing keys with the same name - Use a linter or validator to detect duplicate keys - Merge related properties into a single, unified object structure Example of problematic code: ```json { "codeIndex": { "setting1": "value1" }, // Other settings... "codeIndex": { "setting2": "value2" } } ``` Correct approach: ```json { "codeIndex": { "setting1": "value1", "setting2": "value2" } // Other settings... } ``` This is especially critical in localization files and application configuration where duplicate keys can lead to missing translations or incorrect settings being applied.