Reference Material:

https://aws.amazon.com/efs/faq/
Q: What is Amazon EFS Replication?
EFS Replication can replicate your file system data to another Region or within the same Region without requiring additional infrastructure or a custom process. Amazon EFS Replication automatically and transparently replicates your data to a second file system in a Region or AZ of your choice. You can use the Amazon EFS console, AWS CLI, and APIs to activate replication on an existing file system. EFS Replication is continual and provides a recovery point objective (RPO) and a recovery time objective (RTO) of minutes, helping you meet your compliance and business continuity goals.
https://aws.amazon.com/efs/faq/
During a disaster or fault within an AZ affecting all copies of your data, you might experience loss of data that has not been replicated using Amazon EFS Replication. EFS Replication is designed to meet a recovery point objective (RPO) and recovery time objective (RTO) of minutes. You can use AWS Backup to store additional copies of your file system data and restore them to a new file system in an AZ or Region of your choice. Amazon EFS file system backup data created and managed by AWS Backup is replicated to three AZs and is designed for 99.999999999% (11 nines) durability.