+1, sync replication also reduces availability: any replica downtime becomes write unavailability until you decide that replica is "dead" and stop replicating t

+1, sync replication also reduces availability: any replica downtime becomes write unavailability until you decide that replica is "dead" and stop replicating to it. There's also hybrid setups of sync+async for durability reasons, sync to a single replica so that if your primary db suddenly catches fire you have a replica that's as up to date as possible, then read replicas using async replication.