Pgbouncer performance query

List,

I am trying pgbouncer for inhouse deployment for PostgreSQL 16.

My setup is PostgreSQL VM : 5444 <=> Pgbouncer VM:5444 <===> Clients
(PostgreSQL with IP 10.12.0.2 and Pgbouncer 10.12.0.35 )

Conducted an inhouse benchmark test (pgbench) performed, I have seen
the following results.

On direct hit the DB server handled tps = 162252.508744 (without initial
connection time)
latency average = 1.233 ms (Total time taken around 2 Minutes to
complete)

Through Pgbouncer it handled tps = 25107.166425 only (
without initial connection time)
latency average = 11.949 ms ( Total time taken around 20 Minutes to
complete )

Could someone shed some light on improving the total time taken by
pgbouncer in this scenario ? How can I improve the total time taken
from 20 Minutes to any reasonably good value, say 5 Minutes is it possible
?

I agree when I have increased the concurrent connections to 300
(pgbench -c 300 ) then Direct hit on DB server fails with Error too many
clients as follows

[root(at)pgbouncer ~]# pgbench -c 300 -j 2 -t 100000 -h 10.12.0.2 -p 5444
-U recoil -S recoil
Password:
pgbench (16.9, server 16.3.0)
starting vacuum...end.
pgbench: error: connection to server at "10.12.0.2", port 5444 failed:
FATAL: sorry, too many clients already
pgbench: error: could not create connection for client 134
[root(at)pgbouncer ~]#

I have followed this link for benchmark tests (
https://www.thediscoblog.com/supercharging-postgres-with-pgbouncer)

on Direct hit on DB Server without pgbouncer RESULTS:

[root(at)pgbouncer ~]# pgbench -c 200 -j 2 -t 100000 -h 10.12.0.2 -p 5444 -U
recoil -S recoil
Password:
pgbench (16.9, server 16.3.0)
starting vacuum...end.
transaction type: <builtin: select only>
scaling factor: 500
query mode: simple
number of clients: 200
number of threads: 2
maximum number of tries: 1
number of transactions per client: 100000
number of transactions actually processed: 20000000/20000000
number of failed transactions: 0 (0.000%)
latency average = 1.233 ms
initial connection time = 1549.421 ms
tps = 162252.508744 (without initial connection time)
[root(at)pgbouncer ~]#

*Through Pgbouncer to DB Server*

[root(at)pgbouncer ~]# pgbench -c 300 -j 2 -t 100000 -h localhost -p 5444 -U
recoil -S recoil
Password:
pgbench (16.9, server 16.3.0)
starting vacuum...end.
transaction type: <builtin: select only>
scaling factor: 500
query mode: simple
number of clients: 300
number of threads: 2
maximum number of tries: 1
number of transactions per client: 100000
number of transactions actually processed: 30000000/30000000
number of failed transactions: 0 (0.000%)
latency average = 11.949 ms
initial connection time = 26.699 ms
tps = 25107.166425 (without initial connection time)
[root(at)pgbouncer ~]# date
Thu Jan 22 22:13:46 IST 2026
[root(at)pgbouncer ~]#

*But this takes around 20 Minutes to finish. Is this usual behavior ?
*

my DB VM(RHEL9.4) is 16vCPU, 16GB RAM and

Pgbouncer VM(FreeBSD 14.3) is 8 vCPU and Ram is [root(at)pgbouncer ~]#
sysctl -h hw.physmem
hw.physmem: 17143681024
[root(at)pgbouncer ~]#

TOP usage statistics of pgbouncer vm with 200 clients

last pid: 10020; load averages: 1.23, 0.83, 0.59
up 187+22:53:33 22:59:41
27 processes: 1 running, 20 sleeping, 6 stopped
CPU: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
Mem: 79M Active, 1063M Inact, 1410M Wired, 1030M Buf, 13G Free
Swap: 7068M Total, 7068M Free

*pgbouncer.ini *
[root(at)pgbouncer ~]# grep ^[^\;\;] /usr/local/etc/pgbouncer.ini
[databases]
recoil = host=dbmain.mydomain.in port=5444 dbname=recoil
[users]
[pgbouncer]
logfile = /var/log/pgbouncer/pgbouncer.log
pidfile = /var/run/pgbouncer/pgbouncer.pid
listen_addr = *
listen_port = 5444
auth_type = md5
auth_file = /usr/local/etc/pgbouncer.users
admin_users = myuser
stats_users = myuser,
pool_mode = transaction // *Is this the pool_mode * *I have to use *?
max_prepared_statements = 100
server_reset_query = DISCARD ALL
server_reset_query_always = 1
ignore_startup_parameters = extra_float_digits, options, statement_timeout,
idle_in_transaction_session_timeout

max_client_conn = 5000
default_pool_size = 40
min_pool_size = 20
reserve_pool_size = 10
reserve_pool_timeout = 5
max_db_connections = 900
max_user_connections = 800
server_lifetime = 3600
server_idle_timeout = 60000
[root(at)pgbouncer ~]#

*Any parameters do I need to adjust for better performance in terms of
latency time improvement, kindly guide me*

Best regards,
Krishane