Performance

PerformanceManager reports callback timing for your plugin and memory figures for the runtime.

package dev.example;

import dev.zernyth.api.performance.PerformanceOptions;
import dev.zernyth.api.plugin.JavaPlugin;
import java.time.Duration;

public final class ProfilingPlugin extends JavaPlugin {
    @Override
    public void onEnable() {
        var performance = getServer().getPerformanceManager();
        performance.configure(new PerformanceOptions(true, Duration.ofMillis(5), 100));
        getServer().getScheduler().runTaskTimer(() -> {
            for (var callback : performance.getPluginSnapshot().callbacks()) {
                getLogger().info(callback.kind() + ": " + callback.calls() + " calls, " + callback.slowCalls() + " slow");
            }
            getLogger().info("Heap used: " + performance.getRuntimeMemorySnapshot().heapUsed());
        }, 200, 1200);
    }
}

Guidelines

Never block the server thread. Use AsyncRuntime for I/O and heavy work.
Avoid repeated Dimension chunk checks in hot code: the check walks the native list of loaded chunks.
Do not change configuration from code that runs every tick.
Each scheduler pulse stops admitting server callbacks after a 2 ms budget. A single callback can exceed it.

getDiagnostics() on JavaPlugin returns load, enable and disable timings.