diff --git a/requirements.in b/requirements.in
index 054b46c..cf75b96 100644
--- a/requirements.in
+++ b/requirements.in
@@ -1,10 +1,10 @@
 backoff==2.2.1
 deprecation==2.1.0
-mock==4.0.3
+mock==5.1.0
 monotonic==1.6
 packaging==24.1
-pytest==7.4.4
+pytest==8.3.3
 requests==2.32.3
-flake8==7.1.0
+flake8==7.1.1
 python-dateutil==2.9.0
 python-dotenv==1.0.1
diff --git a/requirements.txt b/requirements.txt
index c18c1de..89d9beb 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,21 +6,21 @@
 #
 backoff==2.2.1
     # via -r requirements.in
-certifi==2024.6.2
+certifi==2024.8.30
     # via requests
 charset-normalizer==3.3.2
     # via requests
 deprecation==2.1.0
     # via -r requirements.in
-flake8==7.1.0
+flake8==7.1.1
     # via -r requirements.in
-idna==3.7
+idna==3.10
     # via requests
 iniconfig==2.0.0
     # via pytest
 mccabe==0.7.0
     # via flake8
-mock==4.0.3
+mock==5.1.0
     # via -r requirements.in
 monotonic==1.6
     # via -r requirements.in
@@ -31,11 +31,11 @@ packaging==24.1
     #   pytest
 pluggy==1.5.0
     # via pytest
-pycodestyle==2.12.0
+pycodestyle==2.12.1
     # via flake8
 pyflakes==3.2.0
     # via flake8
-pytest==7.4.4
+pytest==8.3.3
     # via -r requirements.in
 python-dateutil==2.9.0
     # via -r requirements.in
@@ -45,5 +45,5 @@ requests==2.32.3
     # via -r requirements.in
 six==1.16.0
     # via python-dateutil
-urllib3==2.2.2
+urllib3==2.2.3
     # via requests
diff --git a/rudderstack/analytics/client.py b/rudderstack/analytics/client.py
index 453d045..53bb21f 100644
--- a/rudderstack/analytics/client.py
+++ b/rudderstack/analytics/client.py
@@ -1,4 +1,4 @@
-from datetime import datetime
+from datetime import datetime, timezone
 from uuid import uuid4
 import logging
 import numbers
@@ -245,7 +245,7 @@ def _enqueue(self, msg):
         """Push a new `msg` onto the queue, return `(success, msg)`"""
         timestamp = msg['timestamp']
         if timestamp is None:
-            timestamp = datetime.utcnow().replace(tzinfo=tzutc())
+            timestamp = datetime.now(timezone.utc).replace(tzinfo=tzutc())
         message_id = msg.get('messageId')
         if message_id is None:
             message_id = uuid4()
diff --git a/rudderstack/analytics/consumer.py b/rudderstack/analytics/consumer.py
index 637d7aa..ce8f6ff 100644
--- a/rudderstack/analytics/consumer.py
+++ b/rudderstack/analytics/consumer.py
@@ -8,10 +8,9 @@
 
 from queue import Empty
 
-MAX_MSG_SIZE = 4 << 10 << 10  ## 4 mb
-
-# Our servers only accept batches less than 500KB. Here limit is set slightly
+# Our servers only accept payloads within this limit. Here limit is set slightly
 # lower to leave space for extra data that will be added later, eg. "sentAt".
+MAX_MSG_SIZE = 4 << 10 << 10  ## 4 mb
 BATCH_SIZE_LIMIT = 4 << 10 << 10 ## 4 mb
 
 
diff --git a/rudderstack/analytics/request.py b/rudderstack/analytics/request.py
index d11f19a..67b4f24 100644
--- a/rudderstack/analytics/request.py
+++ b/rudderstack/analytics/request.py
@@ -1,4 +1,4 @@
-from datetime import date, datetime
+from datetime import date, datetime, timezone
 from io import BytesIO
 from gzip import GzipFile
 import logging
@@ -17,7 +17,7 @@ def post(write_key, host=None, gzip=True, timeout=15, proxies=None, **kwargs):
     """Post the `kwargs` to the API"""
     log = logging.getLogger('rudderstack')
     body = kwargs
-    body["sentAt"] = datetime.utcnow().replace(tzinfo=tzutc()).isoformat()
+    body["sentAt"] = datetime.now(timezone.utc).replace(tzinfo=tzutc()).isoformat()
     url = remove_trailing_slash(host or 'https://api.rudderstack.com') + '/v1/batch'
     auth = HTTPBasicAuth(write_key, '')
     data = json.dumps(body, cls=DatetimeSerializer)
diff --git a/rudderstack/analytics/test/test_utils.py b/rudderstack/analytics/test/test_utils.py
index 089800f..fae2b1e 100644
--- a/rudderstack/analytics/test/test_utils.py
+++ b/rudderstack/analytics/test/test_utils.py
@@ -1,4 +1,4 @@
-from datetime import date, datetime, timedelta
+from datetime import date, datetime, timedelta, timezone
 from decimal import Decimal
 import unittest
 
@@ -51,7 +51,7 @@ def test_clean(self):
     def test_clean_with_dates(self):
         dict_with_dates = {
             'birthdate': date(1980, 1, 1),
-            'registration': datetime.utcnow(),
+            'registration': datetime.now(timezone.utc),
         }
         self.assertEqual(dict_with_dates, utils.clean(dict_with_dates))