https://www.postgresql.org/docs/current/postgres-fdw.html
https://www.postgresql.org/docs/current/ddl-foreign-data.html
https://wiki.postgresql.org/wiki/Foreign_data_wrappers

2021
https://www.crunchydata.com/blog/understanding-postgres_fdw
2020
https://towardsdatascience.com/how-to-set-up-a-foreign-data-wrapper-in-postgresql-ebec152827f3

sample

EXTENSION postgres_fdw;

CREATE SERVER foreign_server_prod
        FOREIGN DATA WRAPPER postgres_fdw
        OPTIONS (host 'prod-db-ro.staffing.epam.com', port '5432', dbname 'epm_staf');

CREATE USER MAPPING FOR postgres
        SERVER foreign_server_prod
        OPTIONS (user 'epm_staf_readonly', password 'secert');

CREATE FOREIGN TABLE foreign_table (
        id integer NOT NULL,
        data text
)
        SERVER foreign_server_prod
        OPTIONS (schema_name 'public', table_name 'some_table');