App Server - using an existing database issue

I am able to connect the existing database using psql, but get the following error:
Any hint is greatly appreciated.

The advised configuration raises:
Connection to DB failed. Waiting 1s, then retrying migration…

database: "postgres://not_real:not_real@not_real:54/not_real"

If I changed it to

database:
  jdbc: postgres://not_real:not_real@not_real:54/not_real

[ERROR anvil.app-server.run] #error {
:cause clojure.lang.PersistentArrayMap cannot be cast to java.lang.String
:via
[{:type java.lang.ClassCastException
:message clojure.lang.PersistentArrayMap cannot be cast to java.lang.String
:at [clojure.java.jdbc$get_connection invokeStatic jdbc.clj 381]}]
:trace
[[clojure.java.jdbc$get_connection invokeStatic jdbc.clj 381]
[clojure.java.jdbc$get_connection invoke jdbc.clj 274]
[clojure.java.jdbc$db_query_with_resultset_STAR_ invokeStatic jdbc.clj 1100]
[clojure.java.jdbc$db_query_with_resultset_STAR_ invoke jdbc.clj 1082]
[clojure.java.jdbc$query invokeStatic jdbc.clj 1171]
[clojure.java.jdbc$query invoke jdbc.clj 1133]
[clojure.java.jdbc$query invokeStatic jdbc.clj 1149]
[clojure.java.jdbc$query invoke jdbc.clj 1133]
[migrator.migrations$is_db_empty_QMARK_ invokeStatic migrations.clj 65]
[migrator.migrations$is_db_empty_QMARK_ invoke migrations.clj 63]
[migrator.core$migrate_BANG_$fn__862$fn__864 invoke core.clj 27]
[migrator.core$migrate_BANG_$fn__862 invoke core.clj 26]
[migrator.core$migrate_BANG_ invokeStatic core.clj 25]
[migrator.core$migrate_BANG_ invoke core.clj 20]
[anvil.app_server.run$_main$fn__1706 invoke run.clj 423]
[anvil.app_server.run$_main invokeStatic run.clj 422]
[anvil.app_server.run$_main doInvoke run.clj 224]
[clojure.lang.RestFn applyTo RestFn.java 137]
[anvil.app_server.run main nil -1]]}

Although it doesn’t make sense that jdbc driver is not installed, I installed it according to the instruction:
https://jdbc.postgresql.org/documentation/head/classpath.html

It still doesn’t work.
Any help is greatly appreciated

export CLASSPATH=/home/tony/venv/lib/python3.6/site-packages/anvil_app_server/anvil-app-server.20200515-134353.jar:/home/tony/jdbc/postgresql.jar:.

java -jar /home/tony/venv/lib/python3.6/site-packages/anvil_app_server/anvil-app-server.20200515-134353.jar --app No_background --origin http://45.75.157.108 --database postgres://not_real:My-pass@not_real.db.elephantsql.com:321/not_real