Lead the architectural design and end-to-end implementation of a high-performance OLAP query engine, including a custom JSON-based DSL, eBNF grammar, and SQL generation/optimization for columnar databases (ClickHouse, SingleStore, DuckDB). Requires deep expertise in compiler theory, multi-dimensional data modeling, Java-based microservices (Micronaut/Spring Boot), Project Loom, distributed caching (Redis), JVM tuning, and extensive backend engineering experience (15+ years).