Always implement proper fallback chains for environment variables and handle missing configuration gracefully. When introducing new environment variables, maintain backward compatibility with existing ones, and apply environment-specific behavior conditionally to avoid issues across different deployment contexts. Key practices: - Use fallback chains with multiple environment variable options - Provide sensible defaults or graceful degradation when configuration is missing - Apply conditional logic based on deployment environment (e.g., `IS_DOCKER_HOSTED`) - Maintain backward compatibility when renaming environment variables Example implementation: ```typescript export function resolveLogging(providedLogging?: boolean): boolean { if (providedLogging !== undefined) { return providedLogging; } // Support both new and legacy environment variables if (process.env.LOGGING_LEVEL || process.env.LOG_LEVEL) { return (process.env.LOGGING_LEVEL || process.env.LOG_LEVEL) === 'true'; } // Graceful fallback based on environment return !['test', 'production'].includes(process.env.NODE_ENV); } // Conditional behavior based on deployment context const options = process.env.IS_DOCKER_HOSTED === 'true' ? { priority: command.priority } : {}; ``` For optional services, avoid initialization entirely when configuration is missing rather than using empty defaults, allowing the application to bootstrap gracefully without the optional functionality.