Self-Hosted Instance Configuration

A PowerSync instance is a running deployment of the PowerSync Service: it replicates data from your source database and streams it to clients based on your Sync Streams. When self-hosting, you run the Service in your own infrastructure and configure each instance with a config file, as described below.

Configure Your Instance

A self-hosted instance needs four things before clients can sync:

A connection to your source database, which PowerSync replicates data from. See Source Database Setup for preparing the database.
A bucket storage database, where the PowerSync Service stores the data it prepares for syncing to clients. MongoDB and Postgres are supported.
Client authentication. See Authentication Setup. When getting started, you can use temporary development tokens instead of setting up a full auth provider.
A sync configuration defining what data syncs to which clients, written as Sync Streams.

You define all of these in the main config file, along with some operational settings. We recommend keeping the sync configuration in a separate file that the main config references, though it can also be defined inline. The skeleton below shows the most common options; the Configuration Reference documents all of them.

service.yaml

# Settings for source database replication
replication:
  # Specify database connection details
  # Note only 1 connection is currently supported
  # Multiple connection support is on the roadmap
  connections:
    - type: postgresql
      # The PowerSync server container can access the Postgres DB via the DB's service name.
      # In this case the hostname is pg-db

      # The connection URI or individual parameters can be specified.
      uri: postgresql://postgres:mypassword@pg-db:5432/postgres

      # SSL settings
      sslmode: disable # 'verify-full' (default) or 'verify-ca' or 'disable'
      # Note: 'disable' is only suitable for local/private networks, not for public networks

# Connection settings for bucket storage (MongoDB and Postgres are supported)
storage:
  # Option 1: MongoDB Storage
  type: mongodb
  uri: mongodb://mongo:27017/powersync_demo
  # Use these if authentication is required. The user should have `readWrite` and `dbAdmin` roles
  # username: myuser
  # password: mypassword

  # Option 2: Postgres Storage
  # type: postgresql
  # This accepts the same parameters as a Postgres replication source connection
  # uri: postgresql://powersync_storage_user:secure_password@storage-db:5432/postgres
  # sslmode: disable

# The port which the PowerSync API server will listen on (defaults to 8080)
port: 8080

# Sync configuration (see the sync_config section below)
sync_config:
  path: sync-config.yaml

# Settings for client authentication
client_auth:
  # Enable this if using Supabase Auth
  # supabase: true
  # supabase_jwt_secret: your-secret

  # JWKS URIs can be specified here.
  jwks_uri: http://demo-backend:6060/api/auth/keys

  # JWKS audience
  audience: ['powersync-dev', 'powersync']

# Settings for telemetry reporting
# See https://docs.powersync.com/maintenance-ops/self-hosting/usage-reporting
telemetry:
  # Opt out of reporting anonymized usage metrics to PowerSync telemetry service
  disable_telemetry_sharing: false

# System-level configuration options
system:
  # Service logging configuration
  logging:
    # Log level for the Service logs
    level: info #  'silly', 'debug', 'verbose', 'http', 'info', 'warn', 'error'
    format: text # 'json' or 'text'

Example service.yaml

The config used by our self-host-demo app. Use the demo as a working reference for your own setup.

Supplying the Config File

Both YAML and JSON config files are supported. The PowerSync Service can read the config in three ways:

From a config file mounted on a volume
From an environment variable containing the Base64 encoding of the config file
From a command line parameter (also Base64 encoded)

You can see examples of these methods in the docker-compose file of our self-host-demo app.

Environment Variable Substitution

The config file uses custom tags for environment variable substitution. !env [variable name] substitutes the value of the environment variable named [variable name]. For example, with the environment variable PS_MONGO_URI=mongodb://mongo:27017/powersync, the YAML

service.yaml

storage:
  type: mongodb
  uri: !env PS_MONGO_URI

resolves to uri: mongodb://mongo:27017/powersync. Only environment variables with names starting with PS_ can be substituted.

Configuration Reference

A machine-readable JSON schema of the config file is available, published as @powersync/service-schema.

Add this comment to the top of your YAML config file to get validation and autocomplete in editors that support the YAML language server (for example VS Code with the YAML extension):

# yaml-language-server: $schema=https://unpkg.com/@powersync/service-schema@latest/json-schema/powersync-config.json

The config file supports the following top-level keys, documented in the sections below:

Key	Purpose
`replication`	Source database connection(s) to replicate from
`storage`	Bucket storage database connection
`port`	Port for the PowerSync API server
`sync_config`	Sync Streams (or legacy Sync Rules) definition
`client_auth`	JWT authentication for client connections
`api`	Admin API tokens and performance/safety limits
`telemetry`	Telemetry sharing and Prometheus metrics
`healthcheck`	Health check probe mechanisms
`migrations`	Storage database schema migration behavior
`system`	Service logging
`metadata`	Custom metadata key-value pairs

`replication`

The replication section defines the source database that PowerSync replicates data from. Specify the connection details in replication.connections. Only one connection is currently supported; multiple connection support is on our roadmap. For instructions on preparing your source database, see Source Database Setup.

If you are using hosted Supabase, you will need to enable IPv6 for Docker as per the Docker docs.If your host OS does not support Docker IPv6 (e.g. macOS), run Supabase locally instead.This is because Supabase only allows direct database connections over IPv6. PowerSync cannot connect using the connection pooler.

All connection types support these common options:

string

required

The connection type. One of postgresql, mongodb, mysql, mssql, or convex.

string

default:"default"

Unique identifier for the connection. Optional when only a single connection is present.

string

default:"default"

Additional meta tag for the connection, used for categorization or grouping.

string[]

Block connections to any of these IP ranges. Include local to block anything not in public unicast ranges.

The remaining options depend on the connection type:

Postgres connection options

service.yaml

replication:
  connections:
    - type: postgresql
      uri: postgresql://postgres:mypassword@pg-db:5432/postgres
      sslmode: verify-full

string

Connection URI in the format postgresql://user:password@hostname:5432/database. Individual connection parameters take precedence over values in the URI.

string

Database hostname. Required if not specified in uri.

number

default:"5432"

Database port.

string

Database username. Required if not specified in uri.

string

Database password. Required if not specified in uri.

string

Database name. Required if not specified in uri.

string

default:"verify-full"

SSL mode: verify-full, verify-ca, or disable. disable is only suitable for local/private networks, not for public networks.

string

CA certificate content in PEM format. Required for verify-ca, optional for verify-full.

string

Client certificate content in PEM format, for TLS client authentication.

string

Client private key content in PEM format, for TLS client authentication.

string

Use a servername for TLS that is different from hostname.

string

default:"powersync_"

Prefix for Postgres logical replication slot names and replication stream names.

number

default:"8"

Maximum number of connections to the source database, per Service process.

number

Connection timeout in seconds. Takes precedence over a connect_timeout query parameter in the URI.

number

default:"30"

Idle timeout in seconds for snapshot connection sockets. If the storage database cannot keep up during the initial snapshot, a storage flush can stall the snapshot for longer than this timeout, which closes the source connection mid-snapshot. This appears in the Service logs as Socket timed out errors during the initial snapshot. Increase the timeout if you see these errors.

number

default:"60"

Interval in seconds between source connection heartbeats. Must be between 5 and 60.

MongoDB connection options

service.yaml

replication:
  connections:
    - type: mongodb
      uri: mongodb+srv://myuser:mypassword@cluster0.abcde.mongodb.net/mydatabase
      post_images: auto_configure

string

required

Connection URI in the format mongodb:// or mongodb+srv://. Standard connection options such as connectTimeoutMS, socketTimeoutMS, serverSelectionTimeoutMS, maxPoolSize and maxIdleTimeMS can be set as query parameters in the URI.

string

Database name. Defaults to the database in the URI path.

string

Database username. Defaults to the username in the URI.

string

Database password. Defaults to the password in the URI.

string

default:"off"

Controls how change stream post-images are used: off, auto_configure, or read_only. auto_configure is recommended for new instances. See Post Images for details on each option.

number

default:"60"

Interval in seconds between source connection heartbeats. Must be between 5 and 60.

MySQL connection options

MySQL support is currently in a Beta release.

service.yaml

replication:
  connections:
    - type: mysql
      uri: mysql://repl_user:mypassword@mysql-db:3306/inventory

string

Connection URI in the format mysql://user:password@hostname:3306/database. Individual connection parameters take precedence over values in the URI.

string

Database hostname. Required if not specified in uri.

number

default:"3306"

Database port.

string

Database username. Required if not specified in uri.

string

Database password. Required if not specified in uri.

string

Database name. Required if not specified in uri.

number

default:"1"

Server ID used when connecting as a replication client.

string

CA certificate content in PEM format.

string

Client certificate content in PEM format, for TLS client authentication.

string

Client private key content in PEM format, for TLS client authentication.

number

default:"50"

The combined size in MB of binlog events that can be queued in memory before throttling is applied.

SQL Server connection options

SQL Server support is currently in a Beta release. Also see SQL Server Additional Configuration.

service.yaml

replication:
  connections:
    - type: mssql
      uri: mssql://powersync_user:mypassword@mssql-db:1433/inventory

string

Connection URI in the format mssql://user:password@hostname:1433/database. Individual connection parameters take precedence over values in the URI.

string

Database hostname. Required if not specified in uri.

number

default:"1433"

Database port.

string

Database username. Required if not specified in uri or authentication.

string

Database password. Required if not specified in uri or authentication.

string

Database name. Required if not specified in uri.

string

The database schema to replicate from.

string

CA certificate content in PEM format.

string

Use a servername for TLS that is different from hostname.

object

Alternative authentication configuration, instead of username and password.

Show properties

string

required

Authentication method: default (SQL Server login) or azure-active-directory-service-principal-secret.

object

required

For default: userName and password. For azure-active-directory-service-principal-secret: clientId, clientSecret and tenantId from your registered Azure application.

object

Additional replication settings.

Show properties

number

default:"1000"

Interval in milliseconds to wait between CDC polling cycles.

number

default:"10"

Maximum number of transactions to poll per polling cycle.

boolean

default:"false"

Whether to trust the server certificate. Set to true for local development and self-signed certificates.

number

default:"60"

Interval in seconds between source connection heartbeats. Must be between 5 and 60.

Convex connection options

The Convex replicator is currently released as an experimental feature. See Convex source database setup.

service.yaml

replication:
  connections:
    - type: convex
      deployment_url: https://happy-animal-123.convex.cloud
      deploy_key: !env PS_CONVEX_DEPLOY_KEY

string

required

The URL of your Convex deployment.

string

required

A deploy key for the Convex deployment, used to authenticate against the Convex Streaming Export API.

number

default:"1000"

Interval in milliseconds between polling for new changes.

number

default:"60000"

Timeout in milliseconds for requests to the Convex API.

`storage`

The PowerSync Service requires a storage database to store the data and metadata for buckets. You can use either MongoDB or Postgres for this purpose.

The bucket storage database is separate from your source database.

string

required

The storage backend type: mongodb or postgresql.

number

default:"8"

Maximum number of connections to the storage database, per Service process.

string[]

Block connections to any of these IP ranges. Include local to block anything not in public unicast ranges.

number

default:"2"

Storage version to use when deploying a sync configuration that does not specify a storage version. You typically do not need to change this. See Storage Version for the available versions and how they interact with the sync configuration’s storage_version field.

MongoDB Storage

service.yaml

storage:
  type: mongodb
  uri: mongodb://mongo:27017/powersync_demo

string

required

string

Database name. Defaults to the database in the URI path.

string

Database username. Defaults to the username in the URI. See Required Permissions for the roles the user needs.

string

Database password. Defaults to the password in the URI.

number

default:"0.2"

Throttles the clearing of old bucket data after deploying a new sync configuration, by pausing between batches. The pause is proportional to the previous batch duration. Increase this to reduce the impact of clear operations on the storage cluster, or use 0 to clear as fast as possible. Must be between 0 and 20.

string

Read preference for bulk checksum and bucket data reads: primary, primaryPreferred, secondary, secondaryPreferred, or nearest. If unset, MongoDB driver defaults are used. This is an experimental option and may be removed in a future release.

object

Experimental support for storing large bucket data chunks in S3-compatible object storage instead of MongoDB.

Show properties

string

required

Must be s3.

string

required

Name of the S3 bucket.

string

Region of the S3 bucket.

string

Key prefix for stored objects.

string

Custom endpoint, for S3-compatible object storage providers.

boolean

Use path-style addressing, required by some S3-compatible providers.

string

Access key ID for authentication.

string

Secret access key for authentication.

number

Maximum number of concurrent object storage requests.

number

default:"1024"

Chunks smaller than this byte threshold stay inline in MongoDB instead of being offloaded to object storage.

Required Permissions

The Service creates and manages all collections and indexes in the storage database itself, so no manual schema setup is needed. When authentication is enabled, the user needs the built-in readWrite and dbAdmin roles on the storage database:

readWrite@<storage_database>
dbAdmin@<storage_database>

No access beyond the storage database is required. The readWrite role covers regular operation, including creating and dropping collections and indexes. The dbAdmin role is additionally required for collecting storage size metrics and for dropping the database when an instance is torn down. Create the user with:

use powersync_demo
db.createUser({
  user: "powersync_storage_user",
  pwd: "secure_password",
  roles: ["readWrite", "dbAdmin"]
})

MongoDB authenticates against the database where the user was created, so creating the user in the storage database itself works with the connection URI shown above. If you create the user in a different database, such as admin, add authSource=admin to the connection URI. On MongoDB Atlas, assign the same two roles restricted to the storage database.

Replica Set Requirement

MongoDB requires at least one replica set node. A single node is fine for development/staging environments, but a 3-node replica set is recommended for production deployments. MongoDB Atlas enables replica sets by default for new clusters. However, if you’re using your own environment you can enable this manually by running:

mongosh "mongodb+srv://powersync.abcdef.mongodb.net/" --apiVersion 1 --username myuser --eval 'try{rs.status().ok && quit(0)} catch {} rs.initiate({_id: "rs0", version: 1, members: [{ _id: 0, host : "mongo:27017" }]})'

If you are rolling your own Docker environment, you can include this init script in your docker-compose file to configure a replica set as once-off operation:

docker-compose.yaml

  # Initializes the MongoDB replica set. This service will not usually be actively running
  mongo-rs-init:
    image: mongo:7.0
    depends_on:
      - mongo
    restart: "no"
    entrypoint:
      - bash
      - -c
      - 'sleep 10 && mongosh --host mongo:27017 --eval ''try{rs.status().ok && quit(0)} catch {} rs.initiate({_id: "rs0", version: 1, members: [{ _id: 0, host : "mongo:27017" }]})'''

Postgres Storage

You can use Postgres as an alternative bucket storage database.

service.yaml

storage:
  type: postgresql
  uri: postgresql://powersync_storage_user:secure_password@storage-db:5432/postgres

Postgres storage accepts the same connection options as a Postgres replication connection: uri, hostname, port, username, password, database, sslmode, cacert, client_certificate, client_private_key, tls_servername, slot_name_prefix and connect_timeout. In addition, batch limits can be tuned:

object

Limits for batch operations during replication. Increasing these limits can improve replication performance, at the cost of higher memory usage.

Show properties

number

default:"5000000"

Maximum estimated byte size of operations written in a single transaction.

number

default:"2000"

Maximum number of records written in a single transaction.

number

default:"50000000"

Maximum byte size of current_data documents looked up at a time.

Database Setup

You’ll need to create a dedicated user and schema for PowerSync bucket storage. You can either:

Let PowerSync create the schema (recommended):

CREATE USER powersync_storage_user WITH PASSWORD 'secure_password';
-- The user should only have access to the schema it created
GRANT CREATE ON DATABASE postgres TO powersync_storage_user;

Or manually create the schema:

CREATE USER powersync_storage_user WITH PASSWORD 'secure_password';
CREATE SCHEMA IF NOT EXISTS powersync AUTHORIZATION powersync_storage_user;
GRANT CONNECT ON DATABASE postgres TO powersync_storage_user;
GRANT USAGE ON SCHEMA powersync TO powersync_storage_user;
GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA powersync TO powersync_storage_user;

A demo app with Postgres bucket storage is available here.

Postgres Version Requirements

Separate Postgres servers are required for replication connections (i.e. source database) and bucket storage if using Postgres versions below 14.

Postgres Version	Server configuration
Below 14	Separate servers are required for the source and bucket storage. Replication will be blocked if the same server is detected.
14 and above	The source database and bucket storage database can be on the same server. Using the same database (with separate schemas) is supported but may lead to higher CPU usage. Using separate servers remains an option.

`port`

The port setting determines where clients and tools connect to your instance. Change it if the default conflicts with another service in your deployment.

number

default:"8080"

The port on which the PowerSync API server will listen for connections. Can be specified as a number or string.

`sync_config`

The sync_config section points the Service at your Sync Streams (or legacy Sync Rules) definition, usually a separate file referenced with path:

sync_config:
  path: sync-config.yaml

config:
  edition: 3
streams:
  todos:
    auto_subscribe: true
    query: SELECT * FROM todos WHERE owner_id = auth.user_id()

string

Path to the sync configuration YAML file. Ensure the file is available at that path, e.g. in the same directory as your main config or on a mounted volume.

string

The sync configuration inline as a string, as an alternative to path.

boolean

default:"true"

Whether to exit the process if there is an error parsing the sync configuration.

The top-level sync_rules key is a deprecated alias for sync_config. Use sync_config in new configurations.

`client_auth`

The client_auth section defines how the Service verifies your app’s users when they connect to sync. Clients authenticate with JWTs, which the Service validates using the settings here. For more details, see Client Authentication.

service.yaml

client_auth:
  # Enable this if using Supabase Auth
  # supabase: true
  # supabase_jwt_secret: your-secret

  # Option 1: JWKS URI endpoint
  jwks_uri: http://demo-backend:6060/api/auth/keys

  # Option 2: Static collection of public keys for JWT verification
  # jwks:
  #   keys:
  #     - kty: 'RSA'
  #       n: '[rsa-modulus]'
  #       e: '[rsa-exponent]'
  #       alg: 'RS256'
  #       kid: '[key-id]'

  # JWKS audience
  audience: ['powersync-dev', 'powersync']

string | string[]

URI or array of URIs pointing to JWKS endpoints, used to fetch public keys for JWT verification.

object

Inline JWKS configuration, as an alternative or in addition to jwks_uri.

Show properties

object[]

required

An array of JSON Web Keys (JWKs). Supported key types are RSA (RS256, RS384, RS512), HMAC (HS256, HS384, HS512), OKP (EdDSA with Ed25519 or Ed448) and EC (ES256, ES384, ES512 with curves P-256, P-384 or P-521). See Custom Authentication for details.

boolean

default:"false"

Enables Supabase authentication integration. JWKS details are derived from the Supabase connection. See Supabase Auth.

string

Legacy JWT secret for Supabase authentication (HS256 shared secret).

string[]

Valid audiences for JWT validation.

string[]

IP ranges to reject when resolving JWKS URIs. Include local to block anything not in public unicast ranges.

For production environments, we recommend using JWKS with asymmetric keys (RS256, EdDSA, or ECDSA) rather than shared secrets (HS256). Asymmetric keys provide better security through public/private key separation and easier key rotation. See Custom Authentication for more details.

`api`

The api section protects the Service’s admin API routes with access tokens, and sets limits that protect the Service from excessive load. Configure tokens if you use the PowerSync CLI against this instance; the limits rarely need changing.

string[]

Access tokens for the Service’s admin API routes, provided by clients as a Bearer token. If no tokens are configured, the admin API routes reject all requests.

object

Performance and safety parameters for the API.

Show properties

number

default:"200"

Maximum number of connections (HTTP streams or WebSockets) per API process.

number

default:"10"

Maximum concurrency when fetching data from storage. This should not be significantly more than storage.max_pool_size, otherwise it would block on the pool. Increasing this can significantly increase memory usage in some cases.

number

default:"1000"

Maximum number of buckets for each connection. More buckets increase latency and memory usage. While the actual number is controlled by your sync configuration, this hard limit ensures that the Service errors instead of crashing when the sync configuration is misconfigured.

number

default:"1000"

Related to max_buckets_per_connection, but this limit applies directly to parameter query results, before they are converted into a unique set of buckets.

number

default:"60"

Number of minutes to keep client-requested write checkpoint records. Expired records are removed by the compact job. Must be a positive integer.

number

default:"60"

How long to keep cached bucket counts before refreshing them, in minutes. Bucket counts may be affected by compacting.

`telemetry`

The telemetry section controls the operational metrics the Service shares with PowerSync and exposes for your own monitoring. See Usage Reporting and Monitoring for details.

When true, disables sharing of anonymized usage metrics with the PowerSync telemetry service.

number

Port on which Prometheus metrics will be exposed. When set, metrics will be available on this port for scraping.

`healthcheck`

Configures how health check status is exposed. See Health Checks for details on the available probes and endpoints.

object

Mechanisms for exposing health check data. If this is not configured, the Service defaults to legacy behavior for backwards compatibility (filesystem probes always enabled, plus HTTP probes depending on the Service mode). When probes is configured, each mechanism requires explicit opt-in.

Show properties

boolean

default:"false"

Enables exposing health check status via filesystem files.

boolean

default:"false"

Enables exposing health check status via HTTP endpoints.

`migrations`

The migrations section controls whether the Service updates its bucket storage database schema automatically when a new version starts up. Most deployments can keep the default automatic behavior.

boolean

default:"false"

When true, disables automatic storage database schema migrations on startup. Migrations can then be triggered externally by altering the container command.

`system`

The system section configures how the Service itself runs. Currently this covers logging.

object

Service logging configuration.

Show properties

string

default:"info"

Log level for the Service logs: silly, debug, verbose, http, info, warn, or error. The PS_LOG_LEVEL environment variable takes precedence over this option.

string

Log output format: json or text. Defaults to text, or to json when the NODE_ENV environment variable is set to production. The PS_LOG_FORMAT environment variable takes precedence over this option.

`metadata`

Use metadata to attach custom labels to an instance, for example to tell your staging and production deployments apart in error reports.

object

Custom key-value pairs (string values) that identify this instance. When error reporting to Sentry is enabled by setting the SENTRY_DSN environment variable, these pairs are attached as tags to reported errors.

service.yaml

metadata:
  environment: staging
  region: eu-west-1

Get Started

Configuration Details

Sync Streams & Rules

Client SDKs

Handling Writes

Maintenance & Ops

Integrations

Tools

Resources

Self-Hosted Instance Configuration

Configure Your Instance

Example service.yaml

Supplying the Config File

Environment Variable Substitution

Configuration Reference

`replication`

`storage`

MongoDB Storage

Required Permissions

Replica Set Requirement

Postgres Storage

Database Setup

Postgres Version Requirements

`port`

`sync_config`

`client_auth`

`api`

`telemetry`

`healthcheck`

`migrations`

`system`

`metadata`

​Configure Your Instance

Example service.yaml

​Supplying the Config File

​Environment Variable Substitution

​Configuration Reference

​replication

​storage

​MongoDB Storage

Required Permissions

Replica Set Requirement

​Postgres Storage

Database Setup

Postgres Version Requirements

​port

​sync_config

​client_auth

​api

​telemetry

​healthcheck

​migrations

​system

​metadata

Configure Your Instance

Supplying the Config File

Environment Variable Substitution

Configuration Reference

`replication`

`storage`

MongoDB Storage

Postgres Storage

`port`

`sync_config`

`client_auth`

`api`

`telemetry`

`healthcheck`

`migrations`

`system`

`metadata`