A distributed query engine is provided to aggregate data from and/or query a plurality of micro-services and legacy applications in multi-tenanted system in an extensible, flexible, and standards-compliant way. A plurality of dedicated connectors is provided in the distributed query engine, each providing a defined and dedicated access point to a corresponding micro-service or legacy application. A database store or database management system is associated with a corresponding one of the micro-services or the legacy applications. When a user communicates a query to the distributed query engine via a web user interface or gateway, the distributed query engine identifies one or more of the micro-services and/or legacy applications relevant to fulfilling the query, and converts the query into sub-queries, which are accordingly directed to the micro-services and/or the legacy applications to handle respective sub-queries.