Your community is growing, a modpack needs more memory, or on the contrary the server has plenty of headroom: the Upgrade button in the banner changes plan without reinstalling anything. The world, the plugins, the configuration: everything stays in place, only the resources change.
Choose the new plan
Each card details its memory, cores, disk and price. The difference is settled prorated over what remains in your period: moving up only costs the difference for the remaining days, and the change takes effect immediately after payment, a simple restart applies the new resources.
The advice we repeat often
When in doubt, pick the plan below: the change is immediate and prorated, so there is no risk in starting small. The right indicator is the memory gauge in the banner: if it stays above 85 percent all the time, or if chunks load late during peak hours, it is time to move up. A server that hits the ceiling for one peak evening a week does not need double the memory all year.