How Spring Boot 3 + Apache Calcite Eliminates Cross‑Database Chaos with a Unified Query Layer
This article explains why multi‑source data fragmentation hurts service code, introduces Apache Calcite as a query‑abstraction layer that decouples data location from query logic, and provides step‑by‑step Spring Boot 3 integration, practical code samples, common pitfalls, performance tips, and real‑world scenarios.
