Storage Providers

Flow-Like requires S3-compatible object storage for storing workflow data, execution logs, and content. Three providers are supported natively.

AWS S3

STORAGE_PROVIDER=aws

# Credentials
AWS_ACCESS_KEY_ID=AKIAIOSFODNN7EXAMPLE
AWS_SECRET_ACCESS_KEY=wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY

# Region and endpoint
AWS_REGION=us-east-1
AWS_ENDPOINT=  # Leave empty for AWS S3

# Bucket names
META_BUCKET=flow-like-meta
CONTENT_BUCKET=flow-like-content
LOG_BUCKET=flow-like-logs

S3 Express One Zone (Recommended for Meta Bucket)

S3 Express One Zone is a high-performance, single-AZ storage class ideal for the meta bucket:

• 10x faster than standard S3 (single-digit millisecond latency)
• 50% lower cost per request than standard S3
• Consistent performance for metadata-heavy workloads

Express One Zone bucket names end with --<az-id>--x-s3 (e.g., flow-like-meta--usw2-az1--x-s3).

# Enable S3 Express for meta bucket
META_BUCKET=flow-like-meta--usw2-az1--x-s3
META_BUCKET_EXPRESS_ZONE=true

# Content bucket can also use Express if in same AZ
CONTENT_BUCKET=flow-like-content
CONTENT_BUCKET_EXPRESS_ZONE=false

# Logs bucket (standard S3 is usually sufficient)
LOG_BUCKET=flow-like-logs
LOGS_BUCKET_EXPRESS_ZONE=false

Performance

Use S3 Express One Zone for the meta bucket when your API runs in the same AWS region. The execution state store also uses the meta bucket by default, benefiting from Express performance.

IAM Permissions

The credentials need the following permissions on your buckets:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "s3:GetObject",
        "s3:PutObject",
        "s3:DeleteObject",
        "s3:ListBucket"
      ],
      "Resource": [
        "arn:aws:s3:::flow-like-*",
        "arn:aws:s3:::flow-like-*/*"
      ]
    },
    {
      "Effect": "Allow",
      "Action": [
        "s3express:CreateSession"
      ],
      "Resource": [
        "arn:aws:s3express:*:*:bucket/flow-like-*--*--x-s3"
      ]
    }
  ]
}

Scoped Runtime Credentials (STS AssumeRole)

Flow-Like generates scoped credentials for every execution using STS AssumeRole. This ensures users can only access their own prefix-isolated storage paths, providing strict isolation between users and apps.

STS Compatibility Required

Scoped credentials require credential scoping support from your S3-compatible provider:

• AWS S3 ✅ Full support (STS AssumeRole)
• MinIO ✅ Supported (requires STS configuration)
• Cloudflare R2 ✅ Supported (uses proprietary temp credentials API)
• Hetzner Object Storage ❌ Not supported

Providers without credential scoping support cannot be used with Flow-Like.

# Role to assume for runtime credentials
RUNTIME_ROLE_ARN=arn:aws:iam::123456789012:role/FlowLikeRuntimeRole

The runtime role needs a trust policy allowing the API to assume it:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "AWS": "arn:aws:iam::123456789012:role/FlowLikeApiRole"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

When RUNTIME_ROLE_ARN is set, each execution receives temporary credentials scoped to:

• Read/write the specific app’s data (apps/{app_id}/*)
• Read/write the user’s app data (users/{user_id}/apps/{app_id}/*)
• Write execution logs (runs/{app_id}/*)
• Access temporary storage (tmp/user/{user_id}/apps/{app_id}/*)

Cloudflare R2

R2 is S3-compatible and supports prefix-scoped temporary credentials through Cloudflare’s proprietary API:

STORAGE_PROVIDER=r2

# R2 credentials for S3 API access (from R2 API tokens)
R2_ACCESS_KEY_ID=your-r2-access-key-id
R2_SECRET_ACCESS_KEY=your-r2-secret-access-key

# R2 endpoint (replace with your account ID)
R2_ENDPOINT=https://<account-id>.r2.cloudflarestorage.com

# R2 Temp Credentials API (required for scoped credentials)
R2_ACCOUNT_ID=your-cloudflare-account-id
R2_API_TOKEN=your-cloudflare-api-token

# Bucket names
META_BUCKET=flow-like-meta
CONTENT_BUCKET=flow-like-content
LOG_BUCKET=flow-like-logs

R2 API Token Setup

The API token needs the Workers R2 Storage:Edit permission for the temp credentials API:

1. Go to your Cloudflare Dashboard → Manage Account → API Tokens
2. Create a custom token with:
   • Permissions: Account → Workers R2 Storage → Edit
   • Account Resources: Include your account

How R2 Scoped Credentials Work

Unlike AWS STS, R2 uses Cloudflare’s proprietary temp credentials API which:

• Creates temporary S3-compatible credentials (access key, secret key, session token)
• Supports prefix-scoping via the prefixes parameter
• Returns credentials with configurable TTL (default: 1 hour)

Each execution receives temporary credentials scoped to access only:

• The specific app’s data prefixes
• The user’s app data prefixes
• Execution log paths

MinIO (Self-hosted)

For local development or air-gapped environments:

STORAGE_PROVIDER=aws

# MinIO credentials
AWS_ACCESS_KEY_ID=minioadmin
AWS_SECRET_ACCESS_KEY=minioadmin

# MinIO endpoint
AWS_ENDPOINT=http://minio:9000
AWS_REGION=us-east-1
AWS_USE_PATH_STYLE=true

# Bucket names
META_BUCKET=flow-like-meta
CONTENT_BUCKET=flow-like-content
LOG_BUCKET=flow-like-logs

# STS AssumeRole for scoped credentials
# MinIO requires STS to be enabled: https://min.io/docs/minio/linux/developers/security-token-service.html
RUNTIME_ROLE_ARN=arn:minio:iam:::role/FlowLikeRuntimeRole

To add MinIO to your Docker Compose stack, add this service:

services:
  minio:
    image: minio/minio
    command: server /data --console-address ":9001"
    ports:
      - "9000:9000"
      - "9001:9001"  # Console
    environment:
      MINIO_ROOT_USER: minioadmin
      MINIO_ROOT_PASSWORD: minioadmin
    volumes:
      - minio_data:/data
    networks:
      - flowlike

volumes:
  minio_data:

Azure Blob Storage

STORAGE_PROVIDER=azure

# Azure credentials
AZURE_STORAGE_ACCOUNT_NAME=yourstorageaccount
AZURE_STORAGE_ACCOUNT_KEY=your-access-key

# Container names
AZURE_META_CONTAINER=flow-like-meta
AZURE_CONTENT_CONTAINER=flow-like-content
AZURE_LOG_CONTAINER=flow-like-logs

Creating containers

az storage container create --name flow-like-meta --account-name yourstorageaccount
az storage container create --name flow-like-content --account-name yourstorageaccount
az storage container create --name flow-like-logs --account-name yourstorageaccount

Google Cloud Storage

STORAGE_PROVIDER=gcp

# GCP project
GCS_PROJECT_ID=your-project-id

# Service account JSON (base64 encoded or raw)
GOOGLE_APPLICATION_CREDENTIALS_JSON={"type":"service_account","project_id":"..."}

# Bucket names
GCP_META_BUCKET=flow-like-meta
GCP_CONTENT_BUCKET=flow-like-content
GCP_LOG_BUCKET=flow-like-logs

Service account permissions

The service account needs the Storage Object Admin role on your buckets:

gsutil iam ch serviceAccount:your-sa@project.iam.gserviceaccount.com:objectAdmin gs://flow-like-meta
gsutil iam ch serviceAccount:your-sa@project.iam.gserviceaccount.com:objectAdmin gs://flow-like-content
gsutil iam ch serviceAccount:your-sa@project.iam.gserviceaccount.com:objectAdmin gs://flow-like-logs

Path-style URLs

Some S3-compatible providers (MinIO, R2) require path-style URLs:

AWS_USE_PATH_STYLE=true

This changes requests from:

• Virtual-hosted style: https://bucket.endpoint.com/key
• Path style: https://endpoint.com/bucket/key

Environment Variables Reference

Variable	Description	Default
STORAGE_PROVIDER	Storage backend (aws, r2, azure, gcp)	aws
META_BUCKET	Bucket for app metadata and execution state	Required
CONTENT_BUCKET	Bucket for user content and workflow data	Required
LOG_BUCKET	Bucket for execution logs	Required
META_BUCKET_EXPRESS_ZONE	Enable S3 Express for meta bucket	false
CONTENT_BUCKET_EXPRESS_ZONE	Enable S3 Express for content bucket	false
LOGS_BUCKET_EXPRESS_ZONE	Enable S3 Express for logs bucket	false
RUNTIME_ROLE_ARN	IAM role ARN for scoped runtime credentials (AWS/MinIO)	Optional
R2_ACCESS_KEY_ID	R2 S3-compatible access key	R2 only
R2_SECRET_ACCESS_KEY	R2 S3-compatible secret key	R2 only
R2_ENDPOINT	R2 S3-compatible endpoint URL	R2 only
R2_ACCOUNT_ID	Cloudflare account ID for R2 temp credentials	R2 only
R2_API_TOKEN	Cloudflare API token for R2 temp credentials	R2 only
EXECUTION_STATE_BACKEND	State store backend (postgres, redis, s3)	postgres
AWS_USE_PATH_STYLE	Use path-style URLs (for MinIO/R2)	false