Some parameters specified in postgresql.conf
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shared_buffers = 8GB
checkpoint_timeout = 30min
max_wal_size = 20GB
min_wal_size = 10GB
autovacuum = off

Steps
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-- in publisher
-- using scale factor 100
pgbench -i postgres -p 5432 -s 100
-- using default scale factor, 1
pgbench -i postgres -p 5432

-- create table in publisher and subscriber
CREATE TABLE tbl_empty (a int);

-- create publication
create publication pub for table tbl_empty;

-- create subscription
CREATE SUBSCRIPTION sub CONNECTION 'host=localhost port=5432 dbname=postgres' PUBLICATION pub;"

Then set synchronous replication and restart publisher server.

Run pgbench and record the TPS.

pgbench -b tpcb-like -c 4 -j 4 -T 900 -n postgres


About the test machine
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The processor spec of the test machine is Intel® Xeon® Silver 4210 CPU @2.20GHz with 10 cores/20 threads/2 sockets.