diff --git a/database/schema/schema.sql b/database/schema/schema.sql
index ee7f86e..1885ce1 100644
--- a/database/schema/schema.sql
+++ b/database/schema/schema.sql
@@ -28,6 +28,7 @@ CREATE TABLE users (
     theme VARCHAR(50) DEFAULT 'tokyo-night',
     scan_frequency_minutes INTEGER DEFAULT 60,
     auto_scan_enabled BOOLEAN DEFAULT true,
+    max_devices INTEGER DEFAULT 10,
     created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
     updated_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
 );
@@ -427,10 +428,30 @@ CREATE INDEX idx_sync_conflicts_media_item_id ON sync_conflicts(media_item_id);
 CREATE INDEX idx_sync_conflicts_user_id ON sync_conflicts(user_id);
 CREATE INDEX idx_sync_conflicts_status ON sync_conflicts(resolution_status);
 
+-- Composite indexes for sync queue performance (Phase 7)
+CREATE INDEX idx_sync_queue_device_status_priority ON sync_queue(device_id, status, priority ASC, created_at ASC);
+CREATE INDEX idx_sync_queue_status_priority_created ON sync_queue(status, priority ASC, created_at ASC);
+CREATE INDEX idx_sync_queue_device_created_at ON sync_queue(device_id, created_at DESC);
+
+-- Composite indexes for reading progress performance (Phase 7)
+CREATE INDEX idx_reading_progress_user_last_sync ON reading_progress(user_id, last_sync_timestamp DESC);
+CREATE INDEX idx_reading_progress_media_last_sync ON reading_progress(media_item_id, last_sync_timestamp DESC);
+CREATE INDEX idx_reading_progress_user_sync_source ON reading_progress(user_id, last_sync_source, last_sync_timestamp DESC);
+
+-- Composite indexes for devices (Phase 7)
+CREATE INDEX idx_devices_user_sync_enabled ON devices(user_id, sync_enabled, auto_sync);
+CREATE INDEX idx_devices_user_type ON devices(user_id, device_type);
+CREATE INDEX idx_devices_last_seen ON devices(last_seen DESC) WHERE sync_enabled = true;
+
+-- Composite indexes for annotations (Phase 7)
+CREATE INDEX idx_media_notes_user_media ON media_notes(user_id, media_item_id);
+CREATE INDEX idx_media_highlights_user_media ON media_highlights(user_id, media_item_id);
+
 -- Reading history indexes
 CREATE INDEX idx_reading_history_user_id ON reading_history(user_id);
 CREATE INDEX idx_reading_history_media_item_id ON reading_history(media_item_id);
 CREATE INDEX idx_reading_history_created_at ON reading_history(created_at DESC);
+CREATE INDEX idx_reading_history_user_device_created ON reading_history(user_id, device_id, created_at DESC);
 
 -- ============================================
 -- TRIGGER FUNCTIONS (Phase 1)
@@ -473,12 +494,48 @@ COMMENT ON COLUMN media_items.google_books_id IS 'Google Books identifier for in
 -- - All users default to 'user' role
 -- - Admin users can: create/manage libraries and folders, scan media, modify media metadata, delete media, control library visibility
 -- - Regular users can: view visible libraries, rate media, track reading progress, create notes and highlights, manage their profile
--- - To create first admin: UPDATE users SET role = 'admin' WHERE email = 'your-admin-email';
 -- - Library visibility is controlled through library_visibility table - admins can hide/show libraries per user
 -- - Notes and highlights support position data (page:offset or CFI format) for precise location tracking
 -- - Highlights can have associated notes for detailed annotations
 -- - Backward compatibility views (ebooks, ebook_ratings, ebook_reading_progress, ebook_notes, ebook_highlights) maintain existing API contracts
 
+-- ============================================
+-- PERFORMANCE OPTIMIZATION (Phase 7)
+-- ============================================
+-- NOTE: ALTER SYSTEM commands are commented out for sqlc compatibility.
+-- These should be run manually by DBA or via init script:
+--
+-- Concurrency settings for high-throughput sync operations
+-- ALTER SYSTEM SET max_connections = 200;
+-- ALTER SYSTEM SET shared_buffers = '256MB';
+-- ALTER SYSTEM SET effective_cache_size = '1GB';
+-- ALTER SYSTEM SET maintenance_work_mem = '64MB';
+-- ALTER SYSTEM SET checkpoint_completion_target = 0.9;
+-- ALTER SYSTEM SET wal_buffers = '16MB';
+-- ALTER SYSTEM SET default_statistics_target = 100;
+--
+-- Enable parallel query processing for sync operations
+-- ALTER SYSTEM SET max_parallel_workers_per_gather = 4;
+-- ALTER SYSTEM SET max_parallel_workers = 8;
+-- ALTER SYSTEM SET parallel_setup_cost = 100;
+-- ALTER SYSTEM SET parallel_tuple_cost = 0.1;
+--
+-- Work memory for complex sync queries
+-- ALTER SYSTEM SET work_mem = '16MB';
+--
+-- Background writer optimization for sync queue
+-- ALTER SYSTEM SET bgwriter_delay = 200ms;
+-- ALTER SYSTEM SET bgwriter_lru_maxpages = 200;
+-- ALTER SYSTEM SET bgwriter_lru_multiplier = 2.0;
+
+-- Vacuum and analyze schedule for sync tables (run via cron)
+-- VACUUM ANALYZE sync_queue;
+-- VACUUM ANALYZE reading_progress;
+-- VACUUM ANALYZE sync_conflicts;
+-- VACUUM ANALYZE devices;
+-- REINDEX TABLE CONCURRENTLY sync_queue;
+-- REINDEX TABLE CONCURRENTLY reading_progress;
+
 -- ============================================
 -- SYNC HELPER FUNCTIONS (Phase 1)
 -- ============================================