diff --git a/lib/MockMessagingService/init.lua b/lib/MockMessagingService/init.lua
index 1974cde..f0140da 100644
--- a/lib/MockMessagingService/init.lua
+++ b/lib/MockMessagingService/init.lua
@@ -1,16 +1,5 @@
 local MockMessagingService = {}
 
---[[ TODO constraints:
-
-        [Limit]	                                [Maximum]
-    Size of message	                        1kB
-    Messages sent per game server	        150 + 60 * (number of players in this game server) per minute
-    Messages received per topic	            (10 + 20 * number of servers) per minute
-    Messages received for entire game	    (100 + 50 * number of servers) per minute
-    Subscriptions allowed per game server	5 + 2 * (number of players in this game server)
-
---]]
-
 local function _getOrNew(name)
     local rq = script:FindFirstChild(name, false)
 
diff --git a/plugin/init.server.lua b/plugin/init.server.lua
index afa485e..353bcb6 100644
--- a/plugin/init.server.lua
+++ b/plugin/init.server.lua
@@ -4,18 +4,18 @@ if not plugin then return end
 local toolbar = plugin:CreateToolbar("MockMessagingService plugin")
 local enabled = false
 
-function _clone()
-    _remove()
-    local clone = script.Parent.MessagingService.MockMessagingService:Clone()
-    clone.Parent = game.ServerScriptService.MessagingService
-end
-
-function _remove()
+local function _remove()
     if game.ServerScriptService.MessagingService:FindFirstChild("MockMessagingService") ~= nil then
         game.ServerScriptService.MessagingService.MockMessagingService:Destroy()
     end
 end
 
+local function _clone()
+    _remove()
+    local clone = script.Parent.MessagingService.MockMessagingService:Clone()
+    clone.Parent = game.ServerScriptService.MessagingService
+end
+
 -- TODO: proper icon
 local toggleButton = toolbar:CreateButton("Toggle MMS", "Enables or disables MockMessagingService", "rbxassetid://484838285")
 toggleButton.ClickableWhenViewportHidden = true
@@ -36,11 +36,6 @@ end
 
 toggleButton.Click:Connect(toggleButtonClicked)
 
-plugin.Unloading:Connect(function()
-    enabled = false
-    _remove()
-end)
-
 -- ################## Data exchange logic ##################
 local MMS = game.ServerScriptService:WaitForChild("MessagingService"):WaitForChild("MockMessagingService")
 
@@ -49,25 +44,114 @@ local subscribeRequest: BindableEvent = MMS:WaitForChild("SubscribeRequest")
 
 local subscribedTopics = {}
 
+local function _elapsedSeconds(lastTime)
+    local currentTimestamp = os.time()
+    return currentTimestamp - lastTime
+end
+
+local function _serverCount()
+    return plugin:GetSetting("_serverCount") or 0
+end
+
+-- increase the number of servers currently using MMS by one
+plugin:SetSetting("_serverCount", _serverCount() + 1)
+
+--[[ Constraints:
+
+        [Limit]	                                [Maximum]
+    Size of message	                        1kB
+    Messages sent per game server	        150 + 60 * (number of players in this game server) per minute
+    Messages received per topic	            (10 + 20 * number of servers) per minute
+    Messages received for entire game	    (100 + 50 * number of servers) per minute
+    Subscriptions allowed per game server	5 + 2 * (number of players in this game server)
+
+--]]
+local Constraints = {
+    sentMessages = {
+        max = (150 + 60 * #game.Players:GetPlayers()) / 60,
+        count = 0,
+        lastTime = os.time()
+    },
+    subscriptions = {
+        max = 5 + 2 * #game.Players:GetPlayers(),
+        count = 0
+    },
+    receivedMessagesTopic = {
+        max = (10 + 20 * _serverCount()) / 60,
+        count = 0,
+        lastTime = os.time()
+    },
+    receivedMessagesTotal = {
+        max = (100 + 50 * _serverCount()) / 60,
+        count = 0,
+        lastTime = os.time()
+    }
+}
+
 publishRequest.Event:Connect(function (topic: string, message)
+    -- check if message size exceeds 1kB
+    if string.len(tostring(message)) > 1024 then
+        error("Message size exceeds 1kB")
+    end
+
+    -- check if message limit per game server is reached
+    Constraints.sentMessages.count += 1
+    local elapsed = _elapsedSeconds(Constraints.sentMessages.lastTime)
+    if Constraints.sentMessages.count > Constraints.sentMessages.max * elapsed then
+        error("Message limit per game server per minute reached")
+    end
+
     -- plugin:SetSetting hits disc instead of memory, so it can be slow. Spawn so we don't hang.
     task.spawn(plugin.SetSetting, plugin, topic, message)
+
+    Constraints.lastTimestamp = os.time()
 end)
 
 subscribeRequest.Event:Connect(function (topic: string)
+    -- check if already subscribed to topic
+    if subscribedTopics[topic] ~= nil then return end
+
+    -- check if subscription limit per game server is reached
+    Constraints.subscriptions.count += 1
+    if Constraints.subscriptions.count >= Constraints.subscriptions.max then
+        error("Subscription limit per game server reached")
+    end
+
     table.insert(subscribedTopics, topic)
+
+    Constraints.lastTimestamp = os.time()
 end)
 
 game:GetService("RunService").Heartbeat:Connect(function()
+    -- Check if message limit for entire game is reached
+    local elapsed = _elapsedSeconds(Constraints.receivedMessagesTotal.lastTime)
+    if Constraints.receivedMessagesTotal.count >= Constraints.receivedMessagesTotal.max * elapsed then
+        return
+    end
+
     for i, topic in ipairs(subscribedTopics) do
+        -- check if message limit per topic is reached
+        local elapsed = _elapsedSeconds(Constraints.receivedMessagesTopic.lastTime)
+        if Constraints.receivedMessagesTopic.count >= Constraints.receivedMessagesTopic.max * elapsed then
+            continue
+        end
+
         local data = plugin:GetSetting(topic)
         if data then
             -- we want to clear the setting field even if there's
             -- no one subscribed to this topic ready to accept the data
-            plugin:SetSetting(topic, nil)
+            task.spawn(plugin.SetSetting, plugin, topic, nil)
 
             local callback: BindableEvent = MMS:WaitForChild(topic .. "_CallbackEvent")
             callback:Fire(data)
         end
     end
+end)
+
+-- Unloading
+plugin.Unloading:Connect(function()
+    plugin:SetSetting("_serverCount", _serverCount() - 1)
+
+    enabled = false
+    _remove()
 end)
\ No newline at end of file