Optimize streaming replication because of network latency

Hello,

We’ve added a streaming standby on a gcp container. There’s a lot of network latency between our primary in EU and this standby in South America.
I did a big update on a table ( 4 millions rows) and it generates a lot of lag : more than 5 hours.
The standby has great hardware ressources: cpu, ssd disk and had no load during this update.
How could we handle this lag and have less impact, less lag ?
Basic PG Config:
shared_buffers = 8GB
work_mem = 128MB
max_connections = 600
wal_keep_segments = 1000
wal_sender_timeout = 0
replication_timeout=(not set)
wal_receiver_status_interval=10s
max_wal_senders=20
Checkpoint_timeout = 10min
Max_wal_size= 2GB
min_wal_size= 1GB

Thank you
Mai