· Palaniappan P · 16 min read
AWS Lambda S3 Files: POSIX Mount for S3, ~13× Cheaper Than EFS — and the 6 Limits to Know
AWS Lambda can now mount S3 buckets as a POSIX file system. At roughly $0.023 per GB-month for large files it is about 13× cheaper than EFS — but a 60-second write-back delay, broken advisory locks, and atomic-rename quirks will break naive ports. Here is when to use it, when to wait, and how to wire it up safely.