New serverless pattern: Mount an S3 Bucket as a File System on AWS Lambda

[kasacis]

New Pattern: Mount Amazon S3 Files on AWS Lambda

*Issue #, if available: #3062

Description of changes:

This pattern demonstrates how to mount an Amazon S3 bucket as a file system on an AWS Lambda function using Amazon S3 Files, enabling standard Python file I/O to read S3 data — no S3 SDK calls required.

What's included

• SAM template deploying Lambda, S3 Files file system, mount target, access point, S3 bucket, VPC with private subnet and VPC endpoints (no NAT Gateway)
• Python Lambda handler using pandas to read CSV files via the S3 Files mount at /mnt/s3data
• pandas Lambda layer (Linux x86_64 compatible)
• Unit tests (pytest, no AWS required)
• Sample CSV for integration testing
• Architecture diagram
• Full README with build, deploy, test, and cleanup instructions

Key design decisions

• Uses VPC endpoints (S3 Gateway + S3 Files Interface) instead of NAT Gateway — cheaper and more secure
• pandas layer built with --platform manylinux2014_x86_64 for cross-platform compatibility
• Access point scoped to /lambda root directory

Testing

• Unit tests: pytest src/tests/ -v — 10/10 passing
• Integration tested against a deployed stack in us-east-1

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