Judgment of the Court (Tenth Chamber) of 9 September 2021.#XR v Dopravní podnik hl. m. Prahy, a.s.#Request for a preliminary ruling from the Obvodní soud pro Prahu 9.#Reference for a preliminary ruling – Social policy – Directive 2003/88/EC – Organisation of working time – Concepts of ‘working time’ and ‘rest period’ – Break during which the employee must remain ready to respond to a call-out within a two-minute time limit – Primacy of EU law.#Case C-107/19.