Parallel SQL queries using completable future
Yes, your approach is correct.

However, you parallelize various queries, which probably go to a remote backing database. As you told us nothing about the runtime of these queries, the nature of the database, the complexity of the underlying statements, I can only ask you to measure.

Parallelism induces overhead - in the runtime AND in program complexity. Check, whether it is worth it, and where your bottlenecks lie.

In my experience from enterprise applications, real big data transfers are normally not made better by parallelism, as the bottleneck is often the network between application server and database.