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You can deploy ElectricSQL to and use either an external Postgres or an instance of Fly Postgres as the database for the sync service. This guide covers both scenarios:

  1. deploying the Electric sync service and connecting it to an external Postgres
  2. configuring Fly Postgres and the Electric sync service to connect over Fly's private network

Once you've deployed the Electric sync service on Fly, you will also need to deploy and connect your client app to it.

For more context, see Deployment -> Concepts.

Deploying Electric connected to an external Postgres

Before deploying Electric, you'll need a Postgres database (with logical replication enabled) hosted somewhere Electric can connect to. Many managed database providers support logical replication, see Usage -> Installation -> Postgres for some options. Retrieve your database's connection URI with password included from your provider and use it as the value of the DATABASE_URL variable when setting up the app.

Configure your Fly app

The app config needs to include an http_service with internal port 5133 and a TCP service for Electric's migrations proxy that listens on port 65432 by default. See API -> Sync service to learn about the environment variables used by Electric in detail.

Save the following snippet into a file named fly.toml somewhere on your computer, changing the app name as you see fit:

app = "electric-on-fly-test-app"

image = "electricsql/electric:latest"

AUTH_MODE = "insecure"
DATABASE_URL = "postgresql://..."
ELECTRIC_WRITE_TO_PG_MODE = "direct_writes"
PG_PROXY_PASSWORD = "proxy_password"

# The main Internet-facing service of Electric
# to which clients will be connecting.
internal_port = 5133
force_https = true

interval = "10s"
timeout = "1s"
grace_period = "20s"
method = "GET"
path = "/api/status"

# Service definition for the migrations proxy that runs
# on a separate TCP port.
protocol = "tcp"
internal_port = 65432

port = 65432
handlers = ["pg_tls"]
Secrets and environment variables

Secrets allow sensitive values, such as credentials, to be passed securely to your Fly app. The secret is encrypted and stored in a vault. It is made available to the app as an environment variable.

We're not using secrets in this example to keep things short and simple. As soon as you're ready to take your Fly app from development to production, make sure to replace the DATABASE_URL, PG_PROXY_PASSWORD and AUTH_JWT_KEY environment variables with secrets.

See also Usage -> Authentication -> Secure mode to learn about the secure authentication mode for your production-ready deployment of Electric.


In your terminal, navigate to the directory where fly.toml is located and run fly launch --copy-config --ha=false:

$ fly launch --copy-config --ha=false
An existing fly.toml file was found for app electric-on-fly-test-app
Using build strategies '[the "electricsql/electric" docker image]'.
Remove [build] from fly.toml to force a rescan
Creating app in /path/to/fly-test-app
We're about to launch your app on Here's what you're getting:

Organization: Oleksii Sholik (fly launch defaults to the personal org)
Name: electric-on-fly-test-app (from your fly.toml)
Region: Amsterdam, Netherlands (this is the fastest region for you)
App Machines: shared-cpu-1x, 1GB RAM (most apps need about 1GB of RAM)
Postgres: <none> (not requested)
Redis: <none> (not requested)

? Do you want to tweak these settings before proceeding? No
Created app 'electric-on-fly-test-app' in organization 'personal'
Admin URL:
Wrote config file fly.toml
Validating /path/to/fly-test-app/fly.toml
Platform: machines
✓ Configuration is valid

==> Building image
Searching for image 'electricsql/electric' remotely...
image found: img_lj9x4d2z6lxpwo1k

Watch your deployment at

? Would you like to allocate dedicated ipv4 and ipv6 addresses now? Yes
Allocated dedicated ipv4:
Allocated dedicated ipv6: 2a09:8280:1::37:bcca

This deployment will:
* create 1 "app" machine

No machines in group app, launching a new machine
Finished launching new machines
✔ Machine e784e1e2c642e8 [app] update finished: success

Visit your newly deployed app at

We don't currently support multiple running Electric instances connected to the same database. So it's important to override Fly's default behaviour of creating two machines for a new app by passing the --ha=false flag to fly launch.

Verify app's status using fly app list:

$ fly app list
electric-on-fly-test-app personal deployed machines 1m5s ago

Verify that Electric has successfully initialized its connection to Postres:

$ curl
Connection to Postgres is up!

Deploying Electric connected to Fly Postgres

Follow the offical Fly Postgres docs to set up your database. If you already have an instance of Fly Postgres running, make sure it's configured with wal_level=logical:

$ fly pg -a <pg app name> config update --wal-level logical

wal-level replica logical true

? Are you sure you want to apply these changes? Yes
Performing update...
Update complete!
Please note that some of your changes will require a cluster restart
before they will be applied.
? Restart cluster now? Yes
Identifying cluster role(s)
Machine 148ed127a03de8: primary
Restarting machine 148ed127a03de8
Waiting for 148ed127a03de8 to become healthy (started, 1/3)

Now go back to Configure your Fly app above and modify the contents of the fly.toml file shown there by changing the DATABASE_URL value to use your Fly Postgres instance's connection string and adding DATABASE_USE_IPV6 and DATABASE_REQUIRE_SSL environment variables:

DATABASE_URL = "postgres://postgres:...@<pg-app-name>.flycast:5432"
...the rest of the env vars

Fly Postgres does not support encrypted database connections inside its private 6PN network while Electric enforces encryption by default. The above DATABASE_REQUIRE_SSL setting changes Electric's behaviour by allowing it to fallback to using unencrypted connections.

Connecting the client app to Electric running on Fly

If you don't already have an Electric-enabled client app, follow our Quickstart guide or clone our Basic Items example app and go through its README. In either case, skip the steps that show how to run Postgres and Electric locally.

Create a file named .env.local inside your client app's root directory with the following contents so that electric-sql commands know how to connect to your instance of Electric sync service running on Fly:


# This should be the same password as the one used
# for PG_PROXY_PASSWORD in your fly.toml

If you're wondering why we don't set the ELECTRIC_DATABASE_URL variable here, that's because client commands only connect to the Migrations proxy which is a component of Electric sync service. Learn more about the Migrations proxy's role and how it fits into the bigger picture in our Deployment -> Concepts guide.