CREATE TABLE notifications (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    type VARCHAR(30) NOT NULL,
    reference_id INTEGER NOT NULL,
    message VARCHAR(255) NOT NULL,
    is_read TINYINT(1) NOT NULL DEFAULT 0,
    created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
);

CREATE INDEX idx_notifications_unread ON notifications (is_read, created_at);
CREATE INDEX idx_notifications_type ON notifications (type);