diff --git a/scaler/io/utility.py b/scaler/io/utility.py
index 59e02ebb..682909c4 100644
--- a/scaler/io/utility.py
+++ b/scaler/io/utility.py
@@ -11,6 +11,11 @@
 from scaler.protocol.python.message import PROTOCOL
 from scaler.protocol.python.mixins import Message
 
+try:
+    from collections.abc import Buffer  # type: ignore[attr-defined]
+except ImportError:
+    from typing_extensions import Buffer
+
 
 def get_scaler_network_backend_from_env():
     backend_str = os.environ.get("SCALER_NETWORK_BACKEND", "tcp_zmq")  # Default to tcp_zmq
@@ -51,7 +56,7 @@ def create_sync_object_storage_connector(*args, **kwargs) -> SyncObjectStorageCo
         )
 
 
-def deserialize(data: bytes) -> Optional[Message]:
+def deserialize(data: Buffer) -> Optional[Message]:
     with _message.Message.from_bytes(data, traversal_limit_in_words=CAPNP_MESSAGE_SIZE_LIMIT) as payload:
         if not hasattr(payload, payload.which()):
             logging.error(f"unknown message type: {payload.which()}")
diff --git a/scaler/io/ymq/_ymq.pyi b/scaler/io/ymq/_ymq.pyi
index f27e9b45..4887589f 100644
--- a/scaler/io/ymq/_ymq.pyi
+++ b/scaler/io/ymq/_ymq.pyi
@@ -1,13 +1,12 @@
 # NOTE: NOT IMPLEMENTATION, TYPE INFORMATION ONLY
 # This file contains type stubs for the Ymq Python C Extension module
-import sys
 from enum import IntEnum
 from typing import Callable, Optional, SupportsBytes, Union
 
-if sys.version_info >= (3, 12):
-    from collections.abc import Buffer
-else:
-    Buffer = object
+try:
+    from collections.abc import Buffer  # type: ignore[attr-defined]
+except ImportError:
+    from typing_extensions import Buffer
 
 class Bytes(Buffer):
     data: bytes | None
diff --git a/scaler/io/ymq/pymod_ymq/io_socket.h b/scaler/io/ymq/pymod_ymq/io_socket.h
index ab02f0cb..d2ec8e35 100644
--- a/scaler/io/ymq/pymod_ymq/io_socket.h
+++ b/scaler/io/ymq/pymod_ymq/io_socket.h
@@ -38,9 +38,13 @@ extern "C" {
 static void PyIOSocket_dealloc(PyIOSocket* self)
 {
     try {
-        self->ioContext->removeIOSocket(self->socket);
-        self->ioContext.~shared_ptr();
-        self->socket.~shared_ptr();
+        std::shared_ptr<IOSocket> ioSocket   = std::move(self->socket);
+        std::shared_ptr<IOContext> ioContext = std::move(self->ioContext);
+
+        // this function blocks so it's important to release the GIL
+        Py_BEGIN_ALLOW_THREADS;
+        ioContext->removeIOSocket(ioSocket);
+        Py_END_ALLOW_THREADS;
     } catch (...) {
         PyErr_SetString(PyExc_RuntimeError, "Failed to deallocate IOSocket");
         PyErr_WriteUnraisable((PyObject*)self);
diff --git a/scaler/io/ymq/tcp_client.cpp b/scaler/io/ymq/tcp_client.cpp
index f90d191c..caabdee2 100644
--- a/scaler/io/ymq/tcp_client.cpp
+++ b/scaler/io/ymq/tcp_client.cpp
@@ -70,6 +70,7 @@ void TcpClient::onCreated()
         sock->onConnectionCreated(setNoDelay(sockfd), getLocalAddr(sockfd), getRemoteAddr(sockfd), responsibleForRetry);
         if (_retryTimes == 0) {
             _onConnectReturn({});
+            _onConnectReturn = {};
         }
         return;
     }
@@ -78,6 +79,7 @@ void TcpClient::onCreated()
         _eventLoopThread->_eventLoop.addFdToLoop(sockfd, EPOLLOUT | EPOLLET, this->_eventManager.get());
         if (_retryTimes == 0) {
             _onConnectReturn(std::unexpected {Error::ErrorCode::InitialConnectFailedWithInProgress});
+            _onConnectReturn = {};
         }
         return;
     }
@@ -202,6 +204,7 @@ void TcpClient::onCreated()
     if (myErrno == ERROR_IO_PENDING) {
         if (_retryTimes == 0) {
             _onConnectReturn(std::unexpected {Error::ErrorCode::InitialConnectFailedWithInProgress});
+            _onConnectReturn = {};
         }
         return;
     }
@@ -361,6 +364,10 @@ TcpClient::~TcpClient() noexcept
     if (_retryTimes > 0) {
         _eventLoopThread->_eventLoop.cancelExecution(_retryIdentifier);
     }
+    // TODO: Do we think this is an error? See TcpServer::~TcpServer for detail.
+    if (_onConnectReturn) {
+        _onConnectReturn({});
+    }
 }
 
 }  // namespace ymq
diff --git a/scaler/io/ymq/tcp_server.cpp b/scaler/io/ymq/tcp_server.cpp
index fc49bdaf..4eae0f32 100644
--- a/scaler/io/ymq/tcp_server.cpp
+++ b/scaler/io/ymq/tcp_server.cpp
@@ -158,6 +158,7 @@ int TcpServer::createAndBindSocket()
         );
         CloseAndZeroSocket(server_fd);
         _onBindReturn(std::unexpected(Error {Error::ErrorCode::SetSockOptNonFatalFailure}));
+        _onBindReturn = {};
         return -1;
     }
 
@@ -257,6 +258,7 @@ void TcpServer::onCreated()
 #endif  // _WIN32
 
     _onBindReturn({});
+    _onBindReturn = {};
 }
 
 void TcpServer::onRead()
@@ -404,6 +406,13 @@ TcpServer::~TcpServer() noexcept
         _eventLoopThread->_eventLoop.removeFdFromLoop(_serverFd);
         CloseAndZeroSocket(_serverFd);
     }
+    // TODO: Do we think this is an error? In extreme cases:
+    // bindTo(...);
+    // removeIOSocket(...);
+    // Below callback may not be called.
+    if (_onBindReturn) {
+        _onBindReturn({});
+    }
 }
 
 }  // namespace ymq
diff --git a/tests/pymod_ymq/__init__.py b/tests/pymod_ymq/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/pymod_ymq/test_pymod_ymq.py b/tests/pymod_ymq/test_pymod_ymq.py
new file mode 100644
index 00000000..f1804d52
--- /dev/null
+++ b/tests/pymod_ymq/test_pymod_ymq.py
@@ -0,0 +1,147 @@
+import asyncio
+import unittest
+from scaler.io.ymq import ymq
+from scaler.io.utility import serialize, deserialize
+from scaler.protocol.python.message import TaskCancel
+from scaler.utility.identifiers import TaskID
+
+
+class TestPymodYMQ(unittest.IsolatedAsyncioTestCase):
+    async def test_basic(self):
+        ctx = ymq.IOContext()
+        binder = await ctx.createIOSocket("binder", ymq.IOSocketType.Binder)
+        self.assertEqual(binder.identity, "binder")
+        self.assertEqual(binder.socket_type, ymq.IOSocketType.Binder)
+
+        connector = await ctx.createIOSocket("connector", ymq.IOSocketType.Connector)
+        self.assertEqual(connector.identity, "connector")
+        self.assertEqual(connector.socket_type, ymq.IOSocketType.Connector)
+
+        address = "tcp://127.0.0.1:35793"
+        await binder.bind(address)
+        await connector.connect(address)
+
+        await connector.send(ymq.Message(address=None, payload=b"payload"))
+        msg = await binder.recv()
+
+        assert msg.address is not None
+        self.assertEqual(msg.address.data, b"connector")
+        self.assertEqual(msg.payload.data, b"payload")
+
+    async def test_no_address(self):
+        ctx = ymq.IOContext()
+        binder = await ctx.createIOSocket("binder", ymq.IOSocketType.Binder)
+        connector = await ctx.createIOSocket("connector", ymq.IOSocketType.Connector)
+
+        address = "tcp://127.0.0.1:35794"
+        await binder.bind(address)
+        await connector.connect(address)
+
+        with self.assertRaises(ymq.YMQException) as exc:
+            await binder.send(ymq.Message(address=None, payload=b"payload"))
+        self.assertEqual(exc.exception.code, ymq.ErrorCode.BinderSendMessageWithNoAddress)
+
+    async def test_routing(self):
+        ctx = ymq.IOContext()
+        binder = await ctx.createIOSocket("binder", ymq.IOSocketType.Binder)
+        connector1 = await ctx.createIOSocket("connector1", ymq.IOSocketType.Connector)
+        connector2 = await ctx.createIOSocket("connector2", ymq.IOSocketType.Connector)
+
+        address = "tcp://127.0.0.1:35795"
+        await binder.bind(address)
+        await connector1.connect(address)
+        await connector2.connect(address)
+
+        await binder.send(ymq.Message(b"connector2", b"2"))
+        await binder.send(ymq.Message(b"connector1", b"1"))
+
+        msg1 = await connector1.recv()
+        self.assertEqual(msg1.payload.data, b"1")
+
+        msg2 = await connector2.recv()
+        self.assertEqual(msg2.payload.data, b"2")
+
+    async def test_pingpong(self):
+        ctx = ymq.IOContext()
+        binder = await ctx.createIOSocket("binder", ymq.IOSocketType.Binder)
+        connector = await ctx.createIOSocket("connector", ymq.IOSocketType.Connector)
+
+        address = "tcp://127.0.0.1:35791"
+        await binder.bind(address)
+        await connector.connect(address)
+
+        async def binder_routine(binder: ymq.IOSocket, limit: int) -> bool:
+            i = 0
+            while i < limit:
+                await binder.send(ymq.Message(address=b"connector", payload=f"{i}".encode()))
+                msg = await binder.recv()
+                assert msg.payload.data is not None
+
+                recv_i = int(msg.payload.data.decode())
+                if recv_i - i > 1:
+                    return False
+                i = recv_i + 1
+            return True
+
+        async def connector_routine(connector: ymq.IOSocket, limit: int) -> bool:
+            i = 0
+            while True:
+                msg = await connector.recv()
+                assert msg.payload.data is not None
+                recv_i = int(msg.payload.data.decode())
+                if recv_i - i > 1:
+                    return False
+                i = recv_i + 1
+                await connector.send(ymq.Message(address=None, payload=f"{i}".encode()))
+
+                # when the connector sends `limit - 1`, we're done
+                if i >= limit - 1:
+                    break
+            return True
+
+        binder_success, connector_success = await asyncio.gather(
+            binder_routine(binder, 100), connector_routine(connector, 100)
+        )
+
+        if not binder_success:
+            self.fail("binder failed")
+
+        if not connector_success:
+            self.fail("connector failed")
+
+    async def test_big_message(self):
+        ctx = ymq.IOContext()
+        binder = await ctx.createIOSocket("binder", ymq.IOSocketType.Binder)
+        self.assertEqual(binder.identity, "binder")
+        self.assertEqual(binder.socket_type, ymq.IOSocketType.Binder)
+
+        connector = await ctx.createIOSocket("connector", ymq.IOSocketType.Connector)
+        self.assertEqual(connector.identity, "connector")
+        self.assertEqual(connector.socket_type, ymq.IOSocketType.Connector)
+
+        address = "tcp://127.0.0.1:35792"
+        await binder.bind(address)
+        await connector.connect(address)
+
+        for _ in range(10):
+            await connector.send(ymq.Message(address=None, payload=b"." * 500_000_000))
+            msg = await binder.recv()
+
+            assert msg.address is not None
+            self.assertEqual(msg.address.data, b"connector")
+            self.assertEqual(msg.payload.data, b"." * 500_000_000)
+
+    async def test_buffer_interface(self):
+        msg = TaskCancel.new_msg(TaskID.generate_task_id())
+        data = serialize(msg)
+
+        # verify that capnp can deserialize this data
+        _ = deserialize(data)
+
+        # this creates a copy of the data
+        copy = ymq.Bytes(data)
+
+        # this should deserialize without creating a copy
+        # because ymq.Bytes uses the buffer protocol
+        deserialized: TaskCancel = deserialize(copy)  # type: ignore
+        self.assertEqual(deserialized.task_id, msg.task_id)
diff --git a/tests/pymod_ymq/test_types.py b/tests/pymod_ymq/test_types.py
new file mode 100644
index 00000000..996110b0
--- /dev/null
+++ b/tests/pymod_ymq/test_types.py
@@ -0,0 +1,88 @@
+import unittest
+from enum import IntEnum
+from scaler.io.ymq import ymq
+import array
+
+
+class TestTypes(unittest.TestCase):
+    def test_exception(self):
+        # type checkers misidentify this as "unnecessary" due to the type hints file
+        self.assertTrue(issubclass(ymq.YMQException, Exception))  # type: ignore
+
+        exc = ymq.YMQException(ymq.ErrorCode.CoreBug, "oh no")
+        self.assertEqual(exc.args, (ymq.ErrorCode.CoreBug, "oh no"))
+        self.assertEqual(exc.code, ymq.ErrorCode.CoreBug)
+        self.assertEqual(exc.message, "oh no")
+
+    def test_error_code(self):
+        self.assertTrue(issubclass(ymq.ErrorCode, IntEnum))  # type: ignore
+        self.assertEqual(
+            ymq.ErrorCode.ConfigurationError.explanation(),
+            "An error generated by system call that's likely due to mis-configuration",
+        )
+
+    def test_bytes(self):
+        b = ymq.Bytes(b"data")
+        self.assertEqual(b.len, len(b))
+        self.assertEqual(b.len, 4)
+        self.assertEqual(b.data, b"data")
+
+        # would raise an exception if ymq.Bytes didn't support the buffer interface
+        m = memoryview(b)
+        self.assertTrue(m.obj is b)
+        self.assertEqual(m.tobytes(), b"data")
+
+        b = ymq.Bytes()
+        self.assertEqual(b.len, 0)
+        self.assertTrue(b.data is None)
+
+        b = ymq.Bytes(b"")
+        self.assertEqual(b.len, 0)
+        self.assertEqual(b.data, b"")
+
+        b = ymq.Bytes(array.array("B", [115, 99, 97, 108, 101, 114]))
+        assert b.len == 6
+        assert b.data == b"scaler"
+
+    def test_message(self):
+        m = ymq.Message(b"address", b"payload")
+        assert m.address is not None
+        self.assertEqual(m.address.data, b"address")
+        self.assertEqual(m.payload.data, b"payload")
+
+        m = ymq.Message(address=None, payload=ymq.Bytes(b"scaler"))
+        self.assertTrue(m.address is None)
+        self.assertEqual(m.payload.data, b"scaler")
+
+        m = ymq.Message(b"address", payload=b"payload")
+        assert m.address is not None
+        self.assertEqual(m.address.data, b"address")
+        self.assertEqual(m.payload.data, b"payload")
+
+    def test_io_context(self):
+        ctx = ymq.IOContext()
+        self.assertEqual(ctx.num_threads, 1)
+
+        ctx = ymq.IOContext(2)
+        self.assertEqual(ctx.num_threads, 2)
+
+        ctx = ymq.IOContext(num_threads=3)
+        self.assertEqual(ctx.num_threads, 3)
+
+    # TODO: backporting to 3.8 broke this somehow
+    # it causes a segmentation fault
+    # re-enable once fixed
+    @unittest.skip("causes segmentation fault")
+    def test_io_socket(self):
+        # check that we can't create io socket instances directly
+        self.assertRaises(TypeError, lambda: ymq.IOSocket())  # type: ignore
+
+    def test_io_socket_type(self):
+        self.assertTrue(issubclass(ymq.IOSocketType, IntEnum))  # type: ignore
+
+    def test_bad_socket_type(self):
+        ctx = ymq.IOContext()
+
+        # TODO: should the core reject this?
+        socket = ctx.createIOSocket_sync("identity", ymq.IOSocketType.Uninit)
+        self.assertEqual(socket.socket_type, ymq.IOSocketType.Uninit)