MAPG-185 adapt README

README.md

@@ -46,6 +46,14 @@ One very important variable is `DEV`. This indicates that the application operat
 
 If you install the application in the Docker stack for development (staging) environment, only the variables for external dependencies (API keys, map attribution, etc.) should be adapted. All other variables (for DB connection, static root, mailing, etc.) are fine with the default value.
 
+### (Production only) Create cron job
+
+To maintain database (delete inactive users, old sessions etc.), the command `db:maintain` should be regularly executed. It is recommened to create a cron job that runs every hour:
+
+```
+0 * * * * /path/to/your/installation/mapg db:maintain >>/var/log/cron-mapguesser.log 2>&1
+```
+
 ### Finalize installation
 
 After you set the environment variables in the `.env` file, execute the following command: