Well

A. EFS is dogs*** for this

B. The EFS protocol is NFS, so that's the question.

Apparently EFS is better for storage latency (no personal experience): https://lumigo.io/blog/unlocking-more-serverless-use-cases-w...

But on the other hand EFS blocks Lambda's JVM fast start mode that is based on Firecracker VM snapshots. Not that it matters for Postgres...