Magpie's Song (IronHeart Chronicles Book 1) by Alisson Pang

In the slums of BrightStone, Moon Children are worth less than the scrap they collect to survive. It doesn't matter that these abandoned half-breeds are part-Meridian with their ancestors hailing from the technologically advanced wonder that floats above the once-thriving, now plague-ridden city. Instead they are rejected by both societies and forced to live on the outskirts of civilization, joining clans simply to stay alive. Not to mention their role as Tithe, leading the city's infected citizens deep into the Pits where their disease can be controlled.Nineteen-year-old Raggy Maggy is no different, despite the mysterious heart-shaped panel welded to her chest. Or she wasn't, until her chance discovery of a Meridian-built clockwork dragon—and its murdered owner. When the Inquestors policing the city find Maggy at the scene of the crime, she becomes their prime suspect. An exiled doctor and a clanless Moon Child named Ghost keep her hidden; all she has to do is help them find a cure to the plague they believe was not accidental. Doing so might risk more than her life—but it might be the key to uncovering the truth about the parents, and the past, she knows nothing about.