postgresql - "Too many connections for role" error in Heroku (with Ebean) -

i'm using configuration below ebean, there shouldn't more 20 connections open, limit hobby-basic plan use in heroku. so, heroku throwing error: fatal: many connections role... time time. clues?

db.default.partitioncount=1 db.default.maxconnectionsperpartition=20 db.default.minconnectionsperpartition=2 db.default.acquireincrement=1 db.default.acquireretryattempts=3 db.default.acquireretrydelay=30 seconds db.default.connectiontimeout=30 seconds db.default.idlemaxage=5 minutes db.default.idleconnectiontestperiod=0 db.default.maxconnectionage=15 minutes db.default.initsql="select 1" db.default.releasehelperthreads=0