Amazon Elastic File System (Amazon EFS) now supports NFS version 4 lock upgrading and downgrading functionality. This new capability extends support in Amazon EFS for the NFSv4.1 and NFSv4.0 protocols by allowing you to run applications that upgrade a read lock atomically to a write lock and downgrade a write lock atomically to a read lock. One example is SQLite, a popular library that’s embedded into many applications and programming language tools like Python and PHP.