Since version 2.16
Maintenance Mode
You may want to put one or more of your stores in maintenance mode while you do some maintenance work/deployment tasks on your store(s).
Front-Commerce comes with an API that allows you to put/remove a store in
maintenance mode. To enable the maintenance mode API you need to set the
FRONT_COMMERCE_MAINTENANCE_MODE_AUTHORIZATION_TOKEN environment variable.
.env
FRONT_COMMERCE_MAINTENANCE_MODE_AUTHORIZATION_TOKEN=a-secret-token
Once you have setup the FRONT_COMMERCE_MAINTENANCE_MODE_AUTHORIZATION_TOKEN
environment variable the maintenance mode API will be available after restarting
the server