diff --git a/src/main/java/net/minestom/server/benchmark/BenchmarkManager.java b/src/main/java/net/minestom/server/benchmark/BenchmarkManager.java
index e606bc7ca..e159c7d0a 100644
--- a/src/main/java/net/minestom/server/benchmark/BenchmarkManager.java
+++ b/src/main/java/net/minestom/server/benchmark/BenchmarkManager.java
@@ -3,6 +3,8 @@ package net.minestom.server.benchmark;
 import it.unimi.dsi.fastutil.longs.Long2LongMap;
 import it.unimi.dsi.fastutil.longs.Long2LongOpenHashMap;
 import net.minestom.server.MinecraftServer;
+import net.minestom.server.chat.ChatColor;
+import net.minestom.server.utils.MathUtils;
 import net.minestom.server.utils.time.UpdateOption;
 import net.minestom.server.utils.validate.Check;
 
@@ -80,6 +82,11 @@ public class BenchmarkManager {
         threads.add(threadName);
     }
 
+    /**
+     * Get the memory used by the server in bytes
+     *
+     * @return the memory used by the server
+     */
     public long getUsedMemory() {
         return Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
     }
@@ -88,6 +95,23 @@ public class BenchmarkManager {
         return Collections.unmodifiableMap(resultMap);
     }
 
+    public String getCpuMonitoringMessage() {
+        String benchmarkMessage = "";
+        for (Map.Entry<String, ThreadResult> resultEntry : resultMap.entrySet()) {
+            final String name = resultEntry.getKey();
+            final ThreadResult result = resultEntry.getValue();
+
+            benchmarkMessage += ChatColor.GRAY + name;
+            benchmarkMessage += ": ";
+            benchmarkMessage += ChatColor.YELLOW.toString() + MathUtils.round(result.getCpuPercentage(), 2) + "% CPU ";
+            benchmarkMessage += ChatColor.RED.toString() + MathUtils.round(result.getUserPercentage(), 2) + "% USER ";
+            benchmarkMessage += ChatColor.PINK.toString() + MathUtils.round(result.getBlockedPercentage(), 2) + "% BLOCKED ";
+            benchmarkMessage += ChatColor.BRIGHT_GREEN.toString() + MathUtils.round(result.getWaitedPercentage(), 2) + "% WAITED ";
+            benchmarkMessage += "\n";
+        }
+        return benchmarkMessage;
+    }
+
     private void refreshData() {
         ThreadInfo[] threadInfo = threadMXBean.getThreadInfo(threadMXBean.getAllThreadIds());
         for (ThreadInfo threadInfo2 : threadInfo) {
diff --git a/src/main/java/net/minestom/server/instance/InstanceContainer.java b/src/main/java/net/minestom/server/instance/InstanceContainer.java
index 771da0e16..66816a463 100644
--- a/src/main/java/net/minestom/server/instance/InstanceContainer.java
+++ b/src/main/java/net/minestom/server/instance/InstanceContainer.java
@@ -1,7 +1,5 @@
 package net.minestom.server.instance;
 
-import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
-import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
 import lombok.Setter;
 import net.minestom.server.MinecraftServer;
 import net.minestom.server.data.Data;
@@ -32,6 +30,7 @@ import net.minestom.server.world.DimensionType;
 import net.minestom.server.world.biomes.Biome;
 
 import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.locks.Lock;
@@ -53,8 +52,7 @@ public class InstanceContainer extends Instance {
     private List<SharedInstance> sharedInstances = new CopyOnWriteArrayList<>();
 
     private ChunkGenerator chunkGenerator;
-    // WARNING: need to be synchronized properly
-    private final Long2ObjectMap<Chunk> chunks = new Long2ObjectOpenHashMap<>();
+    private final ConcurrentHashMap<Long, Chunk> chunks = new ConcurrentHashMap<>();
     private final Set<Chunk> scheduledChunksToRemove = new HashSet<>();
 
     private ReadWriteLock changingBlockLock = new ReentrantReadWriteLock();
@@ -407,13 +405,11 @@ public class InstanceContainer extends Instance {
                 e.printStackTrace();
             }
         } else {
-            synchronized (chunks) {
-                final Iterator<Chunk> chunkIterator = chunks.values().iterator();
-                while (chunkIterator.hasNext()) {
-                    final Chunk chunk = chunkIterator.next();
-                    final boolean isLast = !chunkIterator.hasNext();
-                    saveChunkToStorage(chunk, isLast ? callback : null);
-                }
+            final Iterator<Chunk> chunkIterator = chunks.values().iterator();
+            while (chunkIterator.hasNext()) {
+                final Chunk chunk = chunkIterator.next();
+                final boolean isLast = !chunkIterator.hasNext();
+                saveChunkToStorage(chunk, isLast ? callback : null);
             }
         }
     }
@@ -524,9 +520,7 @@ public class InstanceContainer extends Instance {
      */
     private void cacheChunk(Chunk chunk) {
         final long index = ChunkUtils.getChunkIndex(chunk.getChunkX(), chunk.getChunkZ());
-        synchronized (chunks) {
-            this.chunks.put(index, chunk);
-        }
+        this.chunks.put(index, chunk);
     }
 
     @Override