There isn't an explicit concept of priority / resource allocation between queries in Postgres.

However, Postgres does that automatically for certain background processes like autovacuum, background worker etc. by allowing you to configure how fast / slow they go.

You could implicitly influence how fast / slow something goes by setting per role / database parameters and giving less resources to certain types of queries (https://www.postgresql.org/docs/15/sql-alterrole.html) or by using explicit locks + lock_timeout to create some kind of a priority.