[BE-DB-001] backend-database: Add database indexes for performance-critical queries

- Created migration 920_add_performance_indexes.sql
- Added indexes on tracks.status, tracks.user_id, tracks.stream_status
- Added composite index on tracks(user_id, status)
- Added indexes on playlists.is_public, user_sessions.is_active
- Added composite index on user_sessions(user_id, is_active)
- Verified existing indexes on users.email, users.username, tracks.creator_id, playlists.user_id, sessions.user_id

Phase: PHASE-1
Priority: P0
Progress: 11/267 (4.1%)

VEZA_COMPLETE_MVP_TODOLIST.json

@@ -1069,7 +1069,7 @@
       "completion": {
         "completed_at": "2025-12-23T00:46:37Z",
         "actual_hours": 0.5,
-        "commits": [],
+        "commits": ["4daf244"],
         "files_changed": [
           "apps/web/src/features/playlists/services/playlistService.ts",
           "apps/web/src/config/features.ts"
@@ -1133,7 +1133,17 @@
       "description": "Add indexes on frequently queried fields: users.email, users.username, tracks.user_id, tracks.status, playlists.user_id, sessions.user_id, etc.",
       "owner": "backend",
       "estimated_hours": 3,
-      "status": "todo",
+      "status": "completed",
+      "completion": {
+        "completed_at": "2025-12-23T00:47:30Z",
+        "actual_hours": 1.0,
+        "commits": [],
+        "files_changed": [
+          "veza-backend-api/migrations/920_add_performance_indexes.sql"
+        ],
+        "notes": "Created migration 920_add_performance_indexes.sql to add performance-critical indexes. Added indexes on: tracks.status, tracks.user_id, tracks.stream_status, tracks.is_public, composite index on tracks(user_id, status), playlists.is_public, user_sessions.is_active, and composite index on user_sessions(user_id, is_active). Verified that users.email, users.username, tracks.creator_id, playlists.user_id, and sessions.user_id already have indexes in existing migrations. All critical query fields now have appropriate indexes.",
+        "issues_encountered": []
+      },
       "files_involved": [
         {
           "path": "veza-backend-api/migrations/",

veza-backend-api/migrations/920_add_performance_indexes.sql

@@ -0,0 +1,41 @@
+-- 920_add_performance_indexes.sql
+-- Add performance-critical indexes for frequently queried fields
+-- BE-DB-001: Add database indexes for performance-critical queries
+
+-- Index on tracks.status for filtering by status (uploading, processing, ready, error)
+CREATE INDEX IF NOT EXISTS idx_tracks_status ON public.tracks(status) WHERE status IS NOT NULL;
+
+-- Index on tracks.user_id (legacy field, but still used in some queries)
+-- Note: creator_id already has an index (idx_tracks_creator_id)
+CREATE INDEX IF NOT EXISTS idx_tracks_user_id ON public.tracks(user_id) WHERE user_id IS NOT NULL;
+
+-- Composite index for common track queries: user_id + status
+CREATE INDEX IF NOT EXISTS idx_tracks_user_id_status ON public.tracks(user_id, status) WHERE user_id IS NOT NULL AND status IS NOT NULL;
+
+-- Index on tracks.stream_status for filtering by stream processing status
+CREATE INDEX IF NOT EXISTS idx_tracks_stream_status ON public.tracks(stream_status) WHERE stream_status IS NOT NULL;
+
+-- Index on tracks.is_public for public/private filtering (legacy field)
+CREATE INDEX IF NOT EXISTS idx_tracks_is_public ON public.tracks(is_public) WHERE is_public = true;
+
+-- Additional indexes for common query patterns
+
+-- Index on playlists.is_public for public playlist queries
+-- Note: visibility already has an index (idx_playlists_visibility)
+CREATE INDEX IF NOT EXISTS idx_playlists_is_public ON public.playlists(is_public) WHERE is_public = true;
+
+-- Index on user_sessions.is_active for active session lookups
+CREATE INDEX IF NOT EXISTS idx_user_sessions_is_active ON public.user_sessions(is_active) WHERE is_active = true;
+
+-- Index on user_sessions.user_id + is_active for common session queries
+CREATE INDEX IF NOT EXISTS idx_user_sessions_user_id_active ON public.user_sessions(user_id, is_active) WHERE is_active = true;
+
+-- Index on sessions table (if it exists separately from user_sessions)
+-- Note: This uses IF NOT EXISTS to avoid errors if table doesn't exist
+DO $$
+BEGIN
+    IF EXISTS (SELECT 1 FROM information_schema.tables WHERE table_schema = 'public' AND table_name = 'sessions') THEN
+        CREATE INDEX IF NOT EXISTS idx_sessions_user_id_active ON public.sessions(user_id) WHERE revoked_at IS NULL;
+    END IF;
+END $$;
+