Right query to get the current number of connections in a PostgreSQL DB

Question

Which of the following two is more accurate?

select numbackends from pg_stat_database;

select count(*) from pg_stat_activity;

Answer 1

They definitely may give different results. The better one is

select count(*) from pg_stat_activity;

It's because it includes connections to WAL sender processes which are treated as regular connections and count towards max_connections.

See max_wal_senders