What are UPSC's tie-breaker rules when two candidates score equal marks?

UPSC's revised tie-breaker (notified 28 August 2019, formalised 26 February 2020) uses two filters: (1) higher marks in Compulsory Papers + Personality Test combined, then (2) older candidate ranked higher. The pre-2019 three-filter rule has been simplified to this two-step cascade.