# Task timed out after 3.00 seconds while mounting EFS file system. Ensure that the VPC is configured correctly and the EFS file system is accessible from the Lambda function's VPC.

- **ID:** `cloud/aws-efs-mount-timeout-lambda`
- **Domain:** cloud
- **Category:** network_error
- **Verification:** ai_generated
- **Fix Rate:** 82%

## Root Cause

AWS Lambda's EFS mount operation has a hard 3-second timeout; if the EFS file system is not reachable due to missing VPC endpoints, security group rules, or subnet routing, the mount fails.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| AWS Lambda runtime Node.js 18 | active | — | — |
| AWS Lambda runtime Python 3.11 | active | — | — |
| EFS Mount Helper 1.0.0 | active | — | — |

## Workarounds

1. **Verify VPC configuration: ensure Lambda is attached to a private subnet with a NAT gateway or VPC endpoints for EFS (`com.amazonaws.region.elasticfilesystem`), and that the security group allows inbound NFS (port 2049) from the Lambda security group** (90% success)
   ```
   Verify VPC configuration: ensure Lambda is attached to a private subnet with a NAT gateway or VPC endpoints for EFS (`com.amazonaws.region.elasticfilesystem`), and that the security group allows inbound NFS (port 2049) from the Lambda security group
   ```
2. **Check EFS access point policy: ensure the IAM role for Lambda has `elasticfilesystem:ClientMount` permission on the access point ARN** (85% success)
   ```
   Check EFS access point policy: ensure the IAM role for Lambda has `elasticfilesystem:ClientMount` permission on the access point ARN
   ```

## Dead Ends

- **** — The 3-second timeout is hardcoded in the Lambda EFS mount helper and cannot be changed by increasing the function timeout (99% fail)
- **** — The Lambda execution environment does not have permissions or tools to mount EFS manually; only the managed mount helper works (95% fail)