A query is received from a client that specifies at least one database operation implicating data within a first database and within a second database. The first database has a first transaction manager and the second database has a second transaction manager. Thereafter, a plurality of transactions responsive to the query are initiated to access the data within the first database and the second database. Execution of the plurality of transactions are coordinated using the first transaction manager such that commits for both of the first database and the second database are handled by the first transaction manager. Data responsive to the query can then be provided to the client. Related apparatus, systems, techniques and articles are also described.