Vacuum and Materialized view refresh slow

Hello There,

We have postgres 9.6 with 3 slaves replicated in synchronous commit.
we recently migrated to to another cloud provider. Though we have the
same configuration for VMs and postgres, we are experiencing systemwide
slowness with writes to database.

I am more concerned about a scheduled script to vacuum and refresh two
Materialized views after every 5 minutes.
Time to refresh MV and vacuum has increased considerably and during this
time a simple insert takes 10-15 seconds which normally should take
milliseconds whereas with old provider that simple insert used to take not
more than couple of seconds during refresh time.

I have seen the vacuum and refresh MV process showing as waiting for a
{change location} sometimes for a fraction of seconds.

Could I be enlighted about what I can do to improve the performance to make
write faster.

Best regards
Vikas