diff --git a/lib/src/config/app_dependencies.dart b/lib/src/config/app_dependencies.dart
index ee2d104..15b5ffe 100644
--- a/lib/src/config/app_dependencies.dart
+++ b/lib/src/config/app_dependencies.dart
@@ -115,7 +115,21 @@ class AppDependencies {
         }
         return Headline.fromJson(json);
       },
-      (h) => h.toJson(), // toJson already handles DateTime correctly
+      (headline) {
+        final json = headline.toJson();
+        // The database expects source_id and category_id, not nested objects.
+        // We extract the IDs and remove the original objects to match the
+        // schema.
+        if (headline.source != null) {
+          json['source_id'] = headline.source!.id;
+        }
+        if (headline.category != null) {
+          json['category_id'] = headline.category!.id;
+        }
+        json.remove('source');
+        json.remove('category');
+        return json;
+      },
     );
     categoryRepository = _createRepository(
       connection,
@@ -147,7 +161,15 @@ class AppDependencies {
         }
         return Source.fromJson(json);
       },
-      (s) => s.toJson(),
+      (source) {
+        final json = source.toJson();
+        // The database expects headquarters_country_id, not a nested object.
+        // We extract the ID and remove the original object to match the
+        // schema.
+        json['headquarters_country_id'] = source.headquarters?.id;
+        json.remove('headquarters');
+        return json;
+      },
     );
     countryRepository = _createRepository(
       connection,
diff --git a/lib/src/services/database_seeding_service.dart b/lib/src/services/database_seeding_service.dart
index 6ba301d..57eab06 100644
--- a/lib/src/services/database_seeding_service.dart
+++ b/lib/src/services/database_seeding_service.dart
@@ -106,8 +106,8 @@ class DatabaseSeedingService {
           CREATE TABLE IF NOT EXISTS headlines (
             id TEXT PRIMARY KEY,
             title TEXT NOT NULL,
-            source_id TEXT NOT NULL,
-            category_id TEXT NOT NULL,
+            source_id TEXT REFERENCES sources(id),
+            category_id TEXT REFERENCES categories(id),
             image_url TEXT,
             url TEXT,
             published_at TIMESTAMPTZ,
@@ -260,19 +260,10 @@ class DatabaseSeedingService {
           final headline = Headline.fromJson(data);
           final params = headline.toJson();
  
-          // The `source_id` and `category_id` columns are NOT NULL. If a fixture
-          // is missing the nested source or category object, we cannot proceed.
-          if (headline.source == null || headline.category == null) {
-            _log.warning(
-              'Skipping headline fixture with missing source or category ID: '
-              '${headline.title}',
-            );
-            continue;
-          }
- 
           // Extract IDs from nested objects and remove the objects to match schema.
-          params['source_id'] = headline.source!.id;
-          params['category_id'] = headline.category!.id;
+          // These are now nullable to match the schema.
+          params['source_id'] = headline.source?.id;
+          params['category_id'] = headline.category?.id;
           params.remove('source');
           params.remove('category');
  
diff --git a/routes/api/v1/data/index.dart b/routes/api/v1/data/index.dart
index 9384235..87fa33b 100644
--- a/routes/api/v1/data/index.dart
+++ b/routes/api/v1/data/index.dart
@@ -8,6 +8,16 @@ import 'package:ht_shared/ht_shared.dart';
 
 import '../../../_middleware.dart'; // Assuming RequestId is here
 
+/// Converts a camelCase string to snake_case.
+String _camelToSnake(String input) {
+  return input
+      .replaceAllMapped(
+        RegExp(r'(?<!^)(?=[A-Z])'),
+        (match) => '_${match.group(0)}',
+      )
+      .toLowerCase();
+}
+
 /// Handles requests for the /api/v1/data collection endpoint.
 /// Dispatches requests to specific handlers based on the HTTP method.
 Future<Response> onRequest(RequestContext context) async {
@@ -109,10 +119,15 @@ Future<Response> _handleGet(
   final queryParams = context.request.uri.queryParameters;
   final startAfterId = queryParams['startAfterId'];
   final limitParam = queryParams['limit'];
-  final sortBy = queryParams['sortBy'];
+  final sortByParam = queryParams['sortBy'];
   final sortOrderRaw = queryParams['sortOrder']?.toLowerCase();
   final limit = limitParam != null ? int.tryParse(limitParam) : null;
 
+  // Convert sortBy from camelCase to snake_case for the database query.
+  // This prevents errors where the client sends 'createdAt' and the database
+  // expects 'created_at'.
+  final sortBy = sortByParam != null ? _camelToSnake(sortByParam) : null;
+
   SortOrder? sortOrder;
   if (sortOrderRaw != null) {
     if (sortOrderRaw == 'asc') {