Minecraft - Overloaded Server

Render distance
For each player, the server must maintain a loaded area of ​​blocks defined by the render distance; for a render distance of 4, this corresponds to an area with a radius of 4 chunks around the player—that is, a 9×9 grid of 81 chunks—which encompasses a volume of 16×16×256×81 blocks.

Wrong version of the plugin/mod
If you use a version of a plugin that is not intended for the server version you are running, the plugin will typically display error messages. Furthermore, it generates nonsensical requests for the server core; these not only trigger errors but also fail to perform any intended action—instead, they simply slow down the server, as it must also record each error in its log.

Map pre-generation
The map can be restricted to a specific range of chunks and pre-generated; the WorldBorder plugin, for example, can be used for this purpose.

A Large Number of Worlds
Although the Minecraft server strives for optimization and multi-threading, there is still only one main thread that handles the majority of the server's operations.

Other server cores
Other server cores—such as CraftBukkit, Spigot, and especially PaperSpigot—are more highly optimized and offer more options for optimization and better server configuration.

Plugin ClearLagg
The ClearLagg plugin is used to remove or unload unused entities and chunks. Once this operation takes place, the server has more CPU time available to perform operations exclusively for active chunks, entities, and tile entities.

Amount of available RAM
Larger servers require at least 10 GB of RAM to function properly; if the available memory is insufficient or too low, the server is forced to invoke the Garbage Collector (GC) more frequently, which can lead to performance issues.

Low number of server cores
When using the Game Panel service, it is important to ensure sufficient vCPU resources. You must account for the requirements of the database, the operating system, and the application itself. If you are using the "BASIC" tier, it is not recommended to run more than one server. The reason is simple: a single CPU core would have to handle requests from the MC:U application, the operating system, the database, and the Minecraft server simultaneously—a scenario that is far from ideal for a single CPU core.

Poorly optimized plugins
If a plugin that extends server functionality is poorly programmed, it can cause unnecessary server overload. You can find more information using Timings