FATAL: number of requested standby connections exceeds max_wal_senders (currently N)

Root cause

The max_wal_senders parameter in postgresql.conf is too low. Each Debezium connector uses one WAL sender connection.

How to fix

1. Increase max_wal_senders in postgresql.conf (e.g., max_wal_senders = 10).
2. Also ensure max_replication_slots >= number of Debezium connectors.
3. Restart PostgreSQL — max_wal_senders is a postmaster parameter and requires a full server restart (pg_reload_conf() is not sufficient).