AWS S3 Files brings a managed POSIX file system at a fraction of EFS costs. Learn how it works, where the 60-second write-back delay bites you, and how to set it up with Lambda in under two minutes.

AWS Fundamentals offers foundational knowledge and resources for understanding Amazon Web Services (AWS) cloud computing services. From basic concepts like virtual servers and storage to advanced topics like serverless architecture and machine learning on AWS, readers can learn how to leverage the full potential of cloud computing for their applications and businesses.

AWS Fundamentals

AWS S3 Files is a managed POSIX/NFS file system backed by S3 storage, offering up to 13x lower storage costs than EFS ($0.023/GB vs $0.30/GB) for large-file workloads. The post covers how S3 Files works (file system, mount target, access point), the full cost comparison including edge cases where S3 Files is actually more expensive (small files under 1 MiB), the critical 60-second write-back delay that breaks coordination patterns, POSIX limitations (no hard links, no cross-client file locking, non-atomic directory renames), and a step-by-step AWS SAM setup for Lambda including VPC networking, service role, and file system provisioning. A decision table helps choose between S3 Files and EFS based on file size, consistency needs, and concurrency requirements.

AWS S3 Files vs EFS — Cost Comparison, POSIX Limits, and Lambda Setup