Can I upgrade a LightNode VPS for a busy period, then downgrade it?
The short answer
Not if the host uses pay-by-traffic billing: LightNode documents that those hosts cannot be downgraded. Host configuration changes also require the instance to be stopped. Data disks can be expanded, but their capacity cannot be reduced.
In more detail
That makes the starting plan important. If Agency handles normal demand and Premium is needed only for a brief peak, include the cost of keeping the larger configuration in your comparison. Check the resize options for your actual node and billing mode before planning on a later downgrade.
Allow for downtime when changing the host configuration: pause jobs safely, keep a recoverable copy and check the application after restart. Plan data-disk capacity separately, since adding space does not give you an option to shrink it again afterward.