diff --git a/.github/workflows/py-lint.yml b/.github/workflows/py-lint.yml
index a7654269bc..8d5f10ba50 100644
--- a/.github/workflows/py-lint.yml
+++ b/.github/workflows/py-lint.yml
@@ -24,7 +24,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: 3.9
+          python-version: '3.10'
       - name: Install Dependencies
         run: |
           pip install -U pip
@@ -38,7 +38,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: 3.9
+          python-version: '3.10'
       - name: Install Dependencies
         run: |
           pip install -U pip
@@ -52,10 +52,10 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: 3.9
+          python-version: '3.10'
       - name: Install Dependencies
         run: |
           pip install -U pip
           pip install -r requirements/lint.txt
       - name: pyupgrade
-        run: pyupgrade --py39-plus *.py `find pontoon -name \*.py`
+        run: pyupgrade --py310-plus *.py `find pontoon -name \*.py`
diff --git a/Makefile b/Makefile
index ff5620f94a..e9a3b4d9c3 100644
--- a/Makefile
+++ b/Makefile
@@ -119,10 +119,10 @@ flake8:
 	"${DC}" run --rm server flake8 pontoon/
 
 pyupgrade:
-	"${DC}" run --rm server pyupgrade --exit-zero-even-if-changed --py39-plus *.py `find pontoon -name \*.py`
+	"${DC}" run --rm server pyupgrade --exit-zero-even-if-changed --py310-plus *.py `find pontoon -name \*.py`
 
 check-pyupgrade:
-	"${DC}" run --rm server pyupgrade --py39-plus *.py `find pontoon -name \*.py`
+	"${DC}" run --rm server pyupgrade --py310-plus *.py `find pontoon -name \*.py`
 
 black:
 	"${DC}" run --rm server black pontoon/
diff --git a/docker/Dockerfile b/docker/Dockerfile
index 44b4ed2942..32c9ad4a3a 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -1,4 +1,4 @@
-FROM python:3.9-bullseye AS server
+FROM python:3.10-bullseye AS server
 
 ARG USER_ID=1000
 ARG GROUP_ID=1000
diff --git a/pontoon/administration/tests/test_views.py b/pontoon/administration/tests/test_views.py
index 7c69d8248b..f05604b411 100644
--- a/pontoon/administration/tests/test_views.py
+++ b/pontoon/administration/tests/test_views.py
@@ -187,8 +187,8 @@ def test_manage_project_strings_translated_resource(client_superuser):
     project = Project.objects.get(id=project.id)
     assert project.total_strings == strings_count * locales_count
 
-    for l in locales:
-        locale = Locale.objects.get(id=l.id)
+    for loc in locales:
+        locale = Locale.objects.get(id=loc.id)
         assert locale.total_strings == strings_count
 
 
diff --git a/pontoon/administration/views.py b/pontoon/administration/views.py
index e9488edb67..1aa7c38424 100644
--- a/pontoon/administration/views.py
+++ b/pontoon/administration/views.py
@@ -158,7 +158,7 @@ def manage_project(request, slug=None, template="admin_project.html"):
 
                 (
                     ProjectLocale.objects.filter(project=project)
-                    .exclude(locale__pk__in=[l.pk for l in locales])
+                    .exclude(locale__pk__in=[loc.pk for loc in locales])
                     .delete()
                 )
                 for locale in locales:
@@ -167,7 +167,7 @@ def manage_project(request, slug=None, template="admin_project.html"):
                 project_locales = ProjectLocale.objects.filter(project=project)
 
                 # Update readonly flags
-                locales_readonly_pks = [l.pk for l in locales_readonly_form]
+                locales_readonly_pks = [loc.pk for loc in locales_readonly_form]
                 project_locales.exclude(locale__pk__in=locales_readonly_pks).update(
                     readonly=False
                 )
@@ -179,7 +179,7 @@ def manage_project(request, slug=None, template="admin_project.html"):
                 locales_pretranslate_form = form.cleaned_data.get(
                     "locales_pretranslate", []
                 )
-                locales_pretranslate_pks = [l.pk for l in locales_pretranslate_form]
+                locales_pretranslate_pks = [loc.pk for loc in locales_pretranslate_form]
                 project_locales.exclude(locale__pk__in=locales_pretranslate_pks).update(
                     pretranslation_enabled=False
                 )
@@ -244,7 +244,7 @@ def manage_project(request, slug=None, template="admin_project.html"):
             {
                 "name": p.name,
                 # Cannot use values_list() here, because it hits the DB again
-                "locales": [l.pk for l in p.locales.all()],
+                "locales": [loc.pk for loc in p.locales.all()],
             }
         )
 
diff --git a/pontoon/checks/libraries/compare_locales.py b/pontoon/checks/libraries/compare_locales.py
index a05b9ec1c9..999fe35fae 100644
--- a/pontoon/checks/libraries/compare_locales.py
+++ b/pontoon/checks/libraries/compare_locales.py
@@ -28,7 +28,7 @@ def __init__(self, key, raw_val, pre_comment):
 
     @property
     def all(self):
-        return f"%s = %s"
+        return "%s = %s"
 
     def __repr__(self):
         return 'ComparePropertiesEntity<key="{}",raw_val="{}",pre_comment="{}">'.format(
diff --git a/pontoon/contributors/utils.py b/pontoon/contributors/utils.py
index 97c985a2c7..ab679811e9 100644
--- a/pontoon/contributors/utils.py
+++ b/pontoon/contributors/utils.py
@@ -94,11 +94,11 @@ def users_with_translations_counts(
         Prefetch("translators_group__user_set", to_attr="fetched_translators"),
     )
 
-    for l in locales:
-        for user in l.managers_group.fetched_managers:
-            managers[user].add(l.code)
-        for user in l.translators_group.fetched_translators:
-            translators[user].add(l.code)
+    for loc in locales:
+        for user in loc.managers_group.fetched_managers:
+            managers[user].add(loc.code)
+        for user in loc.translators_group.fetched_translators:
+            translators[user].add(loc.code)
 
     # Assign properties to user objects.
     contributors = User.objects.filter(pk__in=user_stats.keys())
diff --git a/pontoon/contributors/views.py b/pontoon/contributors/views.py
index 34c07d9df6..6a64e2ce90 100644
--- a/pontoon/contributors/views.py
+++ b/pontoon/contributors/views.py
@@ -310,7 +310,9 @@ def settings(request):
         user_profile_form = forms.UserProfileForm(instance=profile)
 
     selected_locales = list(profile.sorted_locales)
-    available_locales = Locale.objects.exclude(pk__in=[l.pk for l in selected_locales])
+    available_locales = Locale.objects.exclude(
+        pk__in=[loc.pk for loc in selected_locales]
+    )
 
     default_homepage_locale = Locale(name="Default homepage", code="")
     all_locales = list(Locale.objects.all())
diff --git a/pontoon/pretranslation/transformer.py b/pontoon/pretranslation/transformer.py
index af5338efbd..a4f00d4548 100644
--- a/pontoon/pretranslation/transformer.py
+++ b/pontoon/pretranslation/transformer.py
@@ -1,7 +1,7 @@
 import re
 
 from copy import deepcopy
-from typing import Callable, Optional, cast
+from typing import Callable, cast
 
 from fluent.syntax import ast as FTL
 from fluent.syntax.serializer import serialize_expression
@@ -174,7 +174,7 @@ def __init__(
         self,
         locale: Locale,
         entry: FTL.EntryType,
-        callback: Callable[[str, str], tuple[Optional[str], str]],
+        callback: Callable[[str, str], tuple[str | None, str]],
         preserve_placeables: bool = None,
     ):
         prep = PreparePretranslation(locale)
diff --git a/pontoon/sync/changeset.py b/pontoon/sync/changeset.py
index f4e9d0122f..b607160273 100644
--- a/pontoon/sync/changeset.py
+++ b/pontoon/sync/changeset.py
@@ -38,7 +38,7 @@ def __init__(self, db_project, vcs_project, now, locale=None):
         self.locale = locale
 
         # Store locales and resources for FK relationships.
-        self.locales = {l.code: l for l in Locale.objects.all()}
+        self.locales = {loc.code: loc for loc in Locale.objects.all()}
         self.resources = {r.path: r for r in self.db_project.resources.all()}
 
         self.executed = False
diff --git a/pontoon/sync/core.py b/pontoon/sync/core.py
index b6ff82f227..4954ffc41d 100644
--- a/pontoon/sync/core.py
+++ b/pontoon/sync/core.py
@@ -251,11 +251,7 @@ def update_translated_resources_no_files(db_project, locale, changed_resources):
         # only create TranslatedResources if the file is present in the repository for the locale,
         # which we cannot check without files.
         if not resource.is_asymmetric:
-            log.error(
-                "Unable to calculate stats for asymmetric resource: {resource}.".format(
-                    resource
-                )
-            )
+            log.error(f"Unable to calculate stats for asymmetric resource: {resource}")
             continue
 
         translatedresource, _ = TranslatedResource.objects.get_or_create(
@@ -434,11 +430,11 @@ def get_changed_locales(db_project, locales, now):
 
     # Check if any locale for which the exception was raised hasn't been processed yet.
     # For those locales we can't be sure if a change happened, so we assume it did.
-    for l in error_locale_pks:
-        if l not in changed_locale_pks + unchanged_locale_pks:
+    for loc in error_locale_pks:
+        if loc not in changed_locale_pks + unchanged_locale_pks:
             log.error(
                 "Unable to fetch latest commit hash for locale {locale} in project {project}".format(
-                    locale=Locale.objects.get(pk=l), project=db_project.slug
+                    locale=Locale.objects.get(pk=loc), project=db_project.slug
                 )
             )
             changed_locale_pks.append(locale.pk)
diff --git a/pontoon/sync/tasks.py b/pontoon/sync/tasks.py
index 410918f5ed..e1c0bf63a2 100644
--- a/pontoon/sync/tasks.py
+++ b/pontoon/sync/tasks.py
@@ -212,8 +212,8 @@ def sync_translations(
     # We should also sync files for which source file change - but only for read-only locales.
     # See https://github.com/mozilla/pontoon/issues/2068 for more details.
     if added_and_changed_resources:
-        changed_locales_pks = [l.pk for l in locales]
-        readonly_locales_pks = [l.pk for l in readonly_locales]
+        changed_locales_pks = [loc.pk for loc in locales]
+        readonly_locales_pks = [loc.pk for loc in readonly_locales]
         locales = db_project.locales.filter(
             pk__in=changed_locales_pks + readonly_locales_pks
         )
diff --git a/pontoon/sync/vcs/models.py b/pontoon/sync/vcs/models.py
index f2cf8c292a..7bfac01ade 100644
--- a/pontoon/sync/vcs/models.py
+++ b/pontoon/sync/vcs/models.py
@@ -465,12 +465,12 @@ def resources(self):
                     continue
                 locales = []
 
-            locales = {l for l in locales if l in self.locales}
+            locales = {loc for loc in locales if loc in self.locales}
             self.synced_locales.update(locales)
 
             log.debug(
                 "Detected resource file {} for {}".format(
-                    path, ",".join([l.code for l in locales]) or "source"
+                    path, ",".join([loc.code for loc in locales]) or "source"
                 )
             )
 
diff --git a/pontoon/tags/tests/fixtures/tags.py b/pontoon/tags/tests/fixtures/tags.py
index fab593bc9a..63c2787820 100644
--- a/pontoon/tags/tests/fixtures/tags.py
+++ b/pontoon/tags/tests/fixtures/tags.py
@@ -78,7 +78,7 @@ def _tag_iterator(things, **kwargs):
     # `things` can  be either translations or translated_resources, but
     # they must have their `locale`, `project`, `resource` and
     # `resource.path` denormalized where required.
-    locales = list(l.id for l in kwargs.get("locales", []))
+    locales = list(loc.id for loc in kwargs.get("locales", []))
     projects = list(p.id for p in kwargs.get("projects", []))
     slug = kwargs.get("slug", None)
     path = kwargs.get("path", None)
diff --git a/requirements/default.txt b/requirements/default.txt
index ff12c6a80d..9034ef611c 100644
--- a/requirements/default.txt
+++ b/requirements/default.txt
@@ -1,5 +1,5 @@
 #
-# This file is autogenerated by pip-compile with Python 3.9
+# This file is autogenerated by pip-compile with Python 3.10
 # by the following command:
 #
 #    ./docker/compile_requirements.sh
diff --git a/requirements/dev.txt b/requirements/dev.txt
index 83170673bd..abea031b2e 100644
--- a/requirements/dev.txt
+++ b/requirements/dev.txt
@@ -1,5 +1,5 @@
 #
-# This file is autogenerated by pip-compile with Python 3.9
+# This file is autogenerated by pip-compile with Python 3.10
 # by the following command:
 #
 #    ./docker/compile_requirements.sh
diff --git a/requirements/lint.txt b/requirements/lint.txt
index 8ff427010e..1992d18738 100644
--- a/requirements/lint.txt
+++ b/requirements/lint.txt
@@ -1,5 +1,5 @@
 #
-# This file is autogenerated by pip-compile with Python 3.9
+# This file is autogenerated by pip-compile with Python 3.10
 # by the following command:
 #
 #    ./docker/compile_requirements.sh
@@ -66,7 +66,3 @@ tomli==1.2.2 \
     --hash=sha256:c6ce0015eb38820eaf32b5db832dbc26deb3dd427bd5f6556cf0acac2c214fee \
     --hash=sha256:f04066f68f5554911363063a30b108d2b5a5b1a010aa8b6132af78489fe3aade
     # via black
-typing-extensions==4.5.0 \
-    --hash=sha256:5cb5f4a79139d699607b3ef622a1dedafa84e115ab0024e0d9c044a9479ca7cb \
-    --hash=sha256:fb33085c39dd998ac16d1431ebc293a8b3eedd00fd4a32de0ff79002c19511b4
-    # via black
diff --git a/requirements/test.txt b/requirements/test.txt
index 947cf3739b..268fc70e3c 100644
--- a/requirements/test.txt
+++ b/requirements/test.txt
@@ -1,5 +1,5 @@
 #
-# This file is autogenerated by pip-compile with Python 3.9
+# This file is autogenerated by pip-compile with Python 3.10
 # by the following command:
 #
 #    ./docker/compile_requirements.sh
diff --git a/runtime.txt b/runtime.txt
index 815b82f771..5fa6f4127a 100644
--- a/runtime.txt
+++ b/runtime.txt
@@ -1 +1 @@
-python-3.9.18
+python-3.10.13