1. Identify the source of the PostgreSQL 40001 error. This can be done by running the following command:

SELECT * FROM pg_stat_activity WHERE state = 'idle in transaction';

2. Identify the query that is causing the error. This can be done by running the following command:

SELECT query FROM pg_stat_activity WHERE state = 'idle in transaction';

3. Kill the query that is causing the error. This can be done by running the following command:

SELECT pg_cancel_backend(pid) FROM pg_stat_activity WHERE state = 'idle in transaction';

4. Check the logs to see if the query was successfully killed. This can be done by running the following command:

SELECT * FROM pg_log WHERE message LIKE '%canceled%';

5. If the query was successfully killed, restart the PostgreSQL server. This can be done by running the following command:`sudo service postgresql restart`

6. Monitor the PostgreSQL server for any future errors. This can be done by using an automated database observability tool, such as Datadog. This tool can assist in monitoring and fixing the PostgreSQL 40001 error by providing real-time visibility into the performance of the database, as well as alerting when any errors occur.