The morning rush of the Spring Festival travel season at Nanningdong Railway Station resembles a “symphony” composed of suitcase wheels rolling, broadcast announcements and hurried footsteps. On the platform, the electronic screen flashes striking red characters: Train D8292, stopping for 4 minutes.

　　As the EMU train arriving from Beihai slowly pulls into the platform,   few people notice a man with a black tool bag sprinting against the flow of passengers.   His name is Wei Rongli,   a diagnostic engineer at the Nanning EMU Depot of CR-Nanning. At this moment,   he must complete an “ultimate challenge”   within four minutes—repairing seat 5B  in Car 07.

　　Recently, when everyone’s attention has been focused on the journey home, Wei Rongli and his 15 teammates have been the “invisible people” safeguarding the warmth of that journey. They are not under the spotlight, but in every repaired seat, every tea boiler that flows with hot water again and every power socket restored to electricity,   they leave invisible marks of their work.