diff --git a/backend/apps/ai/models/context.py b/backend/apps/ai/models/context.py
index f94d6810f0..b98d2e1835 100644
--- a/backend/apps/ai/models/context.py
+++ b/backend/apps/ai/models/context.py
@@ -10,6 +10,7 @@
 from apps.common.utils import truncate
 
 logger = logging.getLogger(__name__)
+SOURCE_MAX_LENGTH = 100
 
 
 class Context(TimestampedModel):
@@ -19,7 +20,8 @@ class Context(TimestampedModel):
     entity_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
     entity_id = models.PositiveIntegerField()
     entity = GenericForeignKey("entity_type", "entity_id")
-    source = models.CharField(max_length=100, blank=True, default="")
+    source = models.CharField(
+        max_length=SOURCE_MAX_LENGTH, blank=True, default="")
 
     class Meta:
         db_table = "ai_contexts"
diff --git a/backend/apps/common/utils.py b/backend/apps/common/utils.py
index 4b561670fc..1ce3a9a0f8 100644
--- a/backend/apps/common/utils.py
+++ b/backend/apps/common/utils.py
@@ -12,6 +12,9 @@
 from django.utils.text import Truncator
 from django.utils.text import slugify as django_slugify
 from humanize import intword, naturaltime
+from typing import Optional, Iterable, Any
+from django.http import HttpRequest
+
 
 
 def convert_to_camel_case(text: str) -> str:
@@ -47,7 +50,7 @@ def convert_to_snake_case(text: str) -> str:
     return re.sub(r"(?<!^)(?=[A-Z])", "_", text).lower()
 
 
-def clean_url(url: str) -> str | None:
+def clean_url(url: Optional[str]) -> Optional[str]:
     """Clean a URL by removing whitespace and trailing punctuation.
 
     Args:
@@ -86,7 +89,7 @@ def get_nest_user_agent() -> str:
     return settings.APP_NAME.replace(" ", "-").lower()
 
 
-def get_user_ip_address(request) -> str:
+def get_user_ip_address(request: HttpRequest) -> str:
     """Retrieve the user's IP address from the request.
 
     Args:
@@ -103,24 +106,7 @@ def get_user_ip_address(request) -> str:
     return x_forwarded_for.split(",")[0] if x_forwarded_for else request.META.get("REMOTE_ADDR")
 
 
-def is_valid_json(content: str) -> bool:
-    """Check if content is JSON format.
-
-    Args:
-        content: The content to check
-
-    Returns:
-        bool: True if content is valid JSON, False otherwise
-
-    """
-    try:
-        json.loads(content)
-    except (TypeError, ValueError):
-        return False
-    return True
-
-
-def join_values(fields: list, delimiter: str = " ") -> str:
+def join_values(fields: Iterable[Any], delimiter: str = " ") -> str:
     """Join non-empty field values using a specified delimiter.
 
     Args:
@@ -134,7 +120,7 @@ def join_values(fields: list, delimiter: str = " ") -> str:
     return delimiter.join(field for field in fields if field)
 
 
-def natural_date(value: int | str) -> str:
+def natural_date(value: int | str | datetime) -> str:
     """Convert a date or timestamp into a human-readable format.
 
     Args:
@@ -154,7 +140,7 @@ def natural_date(value: int | str) -> str:
     return naturaltime(dt)
 
 
-def natural_number(value: int, unit=None) -> str:
+def natural_number(value: int, unit: Optional[str] = None) -> str:
     """Convert a number into a human-readable format.
 
     Args:
@@ -211,7 +197,7 @@ def truncate(text: str, limit: int, truncate: str = "...") -> str:
     return Truncator(text).chars(limit, truncate=truncate)
 
 
-def validate_url(url: str) -> bool:
+def validate_url(url: Optional[str]) -> bool:
     """Validate that a URL has proper scheme and netloc.
 
     Args:
diff --git a/backend/apps/github/models/commit.py b/backend/apps/github/models/commit.py
index b5525e56c4..04729b6bf2 100644
--- a/backend/apps/github/models/commit.py
+++ b/backend/apps/github/models/commit.py
@@ -7,6 +7,10 @@
 from apps.common.models import BulkSaveModel, TimestampedModel
 from apps.github.models.common import NodeModel
 
+MAX_SHA_LENGTH = 64
+MESSAGE_PREVIEW_LENGTH = 100
+SHORT_SHA_LENGTH = 7
+
 
 class Commit(BulkSaveModel, NodeModel, TimestampedModel):
     """Commit model."""
@@ -29,7 +33,7 @@ class Meta:
     )
     sha = models.CharField(
         verbose_name="SHA",
-        max_length=64,
+        max_length=MAX_SHA_LENGTH,
         help_text="Git commit SHA hash",
     )
 
@@ -59,8 +63,8 @@ class Meta:
 
     def __str__(self) -> str:
         """Return human-readable representation."""
-        short_sha = self.sha[:7] if self.sha else "unknown"
-        message_preview = self.message[:100] if self.message else "No message"
+        short_sha = self.sha[:SHORT_SHA_LENGTH] if self.sha else "unknown"
+        message_preview = self.message[:MESSAGE_PREVIEW_LENGTH] if self.message else "No message"
         return f"{short_sha}: {message_preview}"
 
     @staticmethod
diff --git a/backend/apps/owasp/models/mixins/project.py b/backend/apps/owasp/models/mixins/project.py
index 515173359a..f20d6a29de 100644
--- a/backend/apps/owasp/models/mixins/project.py
+++ b/backend/apps/owasp/models/mixins/project.py
@@ -9,6 +9,7 @@
 from apps.owasp.models.mixins.common import RepositoryBasedEntityModelMixin
 
 ISSUES_LIMIT = 6
+MAX_HEALTH_SCORE = 100
 RELEASES_LIMIT = 4
 REPOSITORIES_LIMIT = 4
 
@@ -40,7 +41,7 @@ def idx_forks_count(self) -> int:
     def idx_health_score(self) -> float | None:
         """Return health score for indexing."""
         # TODO(arkid15r): Enable real health score in production when ready.
-        return 100 if settings.IS_PRODUCTION_ENVIRONMENT else self.health_score
+        return MAX_HEALTH_SCORE if settings.IS_PRODUCTION_ENVIRONMENT else self.health_score
 
     @property
     def idx_is_active(self) -> bool: