/fly-io

Fly.io Databases & Storage Reference

Table of Contents

• Managed Postgres
• Tigris Object Storage
• Upstash Redis
• Volumes as Storage
• Connection Patterns

Managed Postgres

Fly.io's fully managed PostgreSQL service. Handles provisioning, backups, failover.

fly mpg create                           # Create a new cluster (interactive)
fly mpg list                             # List clusters
fly mpg status <cluster-name>            # Cluster details
fly mpg connect <cluster-name>           # Connect via psql
fly mpg config show <cluster-name>       # Show configuration
fly mpg config update <cluster-name>     # Update configuration

Connection: Set the DATABASE_URL secret to the connection string provided during creation.

fly secrets set DATABASE_URL="postgres://user:pass@my-db.flycast:5432/mydb"

Best practices:

• Use Flycast address for internal connectivity
• Practice disaster recovery by testing backup restoration from the dashboard
• Choose cluster configuration based on workload (CPU, memory, storage)

Extensions: Managed Postgres supports many PostgreSQL extensions. Check fly mpg extensions list for available extensions.

Tigris Object Storage

S3-compatible global object storage, powered by Tigris.

fly storage create                       # Create a Tigris bucket (interactive)
fly storage list                         # List buckets
fly storage dashboard <bucket-name>      # Open Tigris dashboard

Access: Use standard S3 SDKs with Tigris credentials. Credentials are automatically set as secrets:

• BUCKET_NAME
• AWS_ACCESS_KEY_ID
• AWS_SECRET_ACCESS_KEY
• AWS_ENDPOINT_URL_S3
• AWS_REGION

Serve static files from Tigris:

[[statics]]
  guest_path = "/assets"
  url_prefix = "/assets"
  tigris_bucket = "my-assets-bucket"
  index_document = "index.html"

Upstash Redis

Managed Redis via Fly.io's Upstash integration.

fly redis create                         # Create Redis instance
fly redis list                           # List instances
fly redis status <name>                  # Instance details
fly redis dashboard <name>              # Open dashboard

Connection string set automatically as REDIS_URL secret. Accessible over private networking.

Volumes as Storage

Fly Volumes provide NVMe-backed persistent storage mounted into Machines.

fly volumes create mydata --region ord --size 10   # Create 10GB volume
fly volumes list                                    # List volumes
fly volumes show <vol-id>                           # Volume details
fly volumes extend <vol-id> --size 20               # Extend (cannot shrink)
fly volumes fork <vol-id>                           # Copy a volume
fly volumes snapshots list <vol-id>                 # List snapshots
fly volumes snapshots create <vol-id>               # Create on-demand snapshot

Key constraints:

• 1:1 mapping: one volume per Machine, one Machine per volume
• Region-pinned: volume exists on one server in one region
• No automatic replication between volumes
• Max size: 500GB
• Encrypted at rest by default

Auto-extend in fly.toml:

[mounts]
  source = "mydata"
  destination = "/data"
  auto_extend_size_threshold = 80       # Extend at 80% usage
  auto_extend_size_increment = "1GB"
  auto_extend_size_limit = "50GB"

Volume snapshots: Daily automatic snapshots retained for 5 days (configurable 1-60 days). Not a replacement for proper backups. Restore creates a new volume of equal or greater size.

Not available during:

• Docker image builds (fly deploy build phase)
• Release commands (temporary Machine)

Connection Patterns

App to Managed Postgres

# Set connection string as secret
fly secrets set DATABASE_URL="postgres://user:pass@my-db.flycast:5432/mydb"

Use Flycast address for private access with Fly Proxy features. Use .internal address for direct 6PN connection.

App to Redis

# Usually auto-configured, but can set manually
fly secrets set REDIS_URL="redis://default:pass@my-redis.flycast:6379"

App to Tigris

Use S3 SDK with environment variables auto-set by Fly.io:

import boto3

s3 = boto3.client('s3')  # Auto-reads AWS_* env vars
s3.put_object(Bucket=os.environ['BUCKET_NAME'], Key='file.txt', Body=data)

Multi-App Architecture

All apps in an organization share private networking. Typical patterns:

[web app] --flycast--> [api app] --6pn--> [database app]
                           |
                           +--6pn--> [worker app]

• Use Flycast addresses for services that benefit from autostop/autostart
• Use .internal DNS for direct connections (lower latency, no proxy)
• Store connection info in secrets, not hardcoded