As a Staff Platform Engineer on Core Platform, you will own one of the primitives at the heart of Charlie Health''s replatforming: the federated GraphQL front door, the event substrate that carries every signal, the identity layer for humans and AI agents, or the real-time world model state layer that gives our services and agents a live picture of care. Depth in at least one of these areas, enough to own it end to end: GraphQL federation, real-time stream processing (Flink, Spark, KsqlDB, or similar), graph databases (Memgraph, Neo4j, Amazon Neptune, Dgraph, or similar), or authorization systems with ReBAC and RBAC models (Zanzibar, OpenFGA, Cedar, or similar).