Use environment variables to control application behavior and ensure configuration changes are properly synchronized between in-memory state and persistent storage. When configuration depends on environment context, check for relevant environment variables first before falling back to defaults. This prevents inconsistencies where in-memory configuration differs from persisted configuration, and allows for environment-specific behavior without hardcoding values. Example patterns: ```typescript // Check environment variable before generating defaults const key = process.env.GOOSE_SERVER__SECRET_KEY || (process.env.GOOSE_EXTERNAL_BACKEND ? 'test' : crypto.randomBytes(32).toString('hex')); // Enable development features via environment if (process.env.ENABLE_DEV_UPDATES === 'true') { autoUpdater.forceDevUpdateConfig = true; } ``` When modifying configuration in memory, ensure changes are also reflected in the persistent storage layer to maintain consistency, or clearly document when temporary in-memory modifications are intentional.