Never have query APIs on your operational databases. Either use a read-only slave, or another database filled through an ETL process. This allows you to refacto

Never have query APIs on your operational databases. Either use a read-only slave, or another database filled through an ETL process. This allows you to refactor your main database, without impacting your API. Also you avoid the performance impact of the APIs on your main database. As an alternative for SQL you can consider oData, it's standardized REST compatible generic query language, similar to graphql, but supported in BI tooling like PowerBI, tableau and excel.