Summary: Logical replication in Neon requires enabling it per project, which permanently changes wal_level to logical and restarts all computes. Use this page when configuring Neon as a publisher or subscriber. It covers Neon-specific constraints: inactive replication slots are removed after ~40 hours, subscribers prevent scale-to-zero, and max_wal_senders and max_replication_slots are both set to 10. Supported decoder plugins are pgoutput and wal2json.

Information about logical replication specific to Neon

This topic outlines information about logical replication specific to Neon, including important notices.

When replicating data from Neon, enable logical replication on your Neon project. When replicating data to Neon, enable it on the source database instead.

Important: Enabling logical replication changes the PostgreSQL wal_level setting from replica to logical for all databases in your Neon project. This allows Postgres to record the row-level WAL detail required for logical decoding. Once changed, it cannot be reverted. Enabling logical replication also restarts all computes, so active connections will be dropped and have to reconnect.

Console

1. Select your project in the Neon Console.
2. On the Project Dashboard, select Settings.
3. Select Postgres, then Logical replication.
4. Click Enable to enable logical replication.

CLI

Use the Neon CLI projects update command with --enable-logical-replication. Replace $PROJECT_ID with your project ID. The --yes flag skips the confirmation prompt.

neon projects update $PROJECT_ID --enable-logical-replication --yes

API

Use the Update project endpoint to enable logical replication programmatically. Replace $PROJECT_ID with your project ID.

curl -X PATCH 'https://console.neon.tech/api/v2/projects/$PROJECT_ID' \
  -H 'Accept: application/json' \
  -H "Authorization: Bearer $NEON_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
  "project": {
    "settings": {
      "enable_logical_replication": true
    }
  }
}'

You can verify that logical replication is enabled by running the following query:

SHOW wal_level;
 wal_level
-----------
 logical

To avoid potential issues, please review the following notices carefully before using logical replication in Neon.

These notices apply when replicating data from Neon (Neon as the publisher):

• Scale to zero and compute usage: While a logical replication subscriber is connected, your Neon compute stays active and will not scale to zero. Neon does not "disable" scale to zero; the database is simply always active because replication keeps it in use, so the compute never becomes idle. This results in ongoing compute usage and can significantly affect your bill. For details, see Logical replication and scale to zero. If you are optimizing costs, see also Cost optimization.
• Removal of inactive replication slots: To prevent storage bloat, **Neon automatically removes inactive replication slots after approximately 40 hours. Please see Unused replication slots for more information.
• Branch restore removes replication slots: Restoring a branch will delete all replication slots on that branch. Replication slots are not automatically re-created during the restore process.

• Before dropping a database in response to a user issued DROP DATABASE command or operation, Neon will drop any logical replication subscriptions defined in the database.
• To prevent issues due to unintended duplication of logical replication subscriptions, subscriptions defined on a parent branch are not duplicated on child branches; they are dropped from child branches before the compute associated with the child branch starts. This applies to all branching contexts where logical replication subscriptions could be duplicated on a child branch, including creating a child branch, resetting a child branch, and restoring a child branch.

Neon's Scale to Zero feature suspends a compute after 300 seconds (5 minutes) of inactivity. When you replicate data from Neon (Neon as publisher), a connected logical replication subscriber keeps the database in use, so the compute never becomes idle. Neon therefore does not suspend the compute; it remains active at all times while subscribers are connected. This applies only when Neon is the publisher (replicating from Neon to an external destination), not when Neon is the subscriber (replicating into Neon from an external source). Neon determines whether there are active replication connections by checking for walsender processes using the following query:

SELECT *
FROM pg_stat_replication
WHERE application_name != 'walproposer';

If the count is greater than 0, a Neon compute where the publishing Postgres instance runs will not be suspended.

To prevent storage bloat, **Neon automatically removes inactive replication slots after approximately 40 hours.

An inactive replication slot is one that doesn't acknowledge flush_lsn progress for more than approximately 40 hours. This is the same flush_lsn value found in the pg_stat_replication view in your Neon database.

An inactive replication slot can be the result of a dead subscriber, where the replication slot has not been removed after a subscriber is deactivated or becomes unavailable. An inactive replication slot can also result from a long replication delay configured on the subscriber. For example, subscribers like Fivetran or Airbyte let you to configure the replication frequency or set a replication delay to minimize usage.

• If replication frequency configured on the subscriber is more than 40 hours, you can prevent replication slots from being dropped by changing the replication frequency to less than 40 hours.

  This will ensure that your subscriber reports flush_lsn progress more frequently than every 40 hours. If increasing replication frequency is not possible, please contact Neon Support for alternatives.

• If using Debezium, set lsn.flush.mode to connector so that the connector reports flush_lsn progress. (The older property flush.lsn.source=true is deprecated but is automatically mapped to lsn.flush.mode=connector for backward compatibility.) For other subscriber platforms, check for an equivalent setting to make sure it's configured to acknowledge progress on the subscriber.

If you find that a replication slot was removed and you need to add it back, please see Create a replication slot for instructions or refer to the replication slot creation instructions for your subscriber.

It is recommended that you create a dedicated Postgres role for replicating data from Neon to a subscriber. This role must have the REPLICATION privilege. The default Postgres role created with your Neon project and roles created using the Neon Console, CLI, or API are granted membership in the neon_superuser role, which has the required REPLICATION privilege. Roles created via SQL do not have this privilege, and the REPLICATION privilege cannot be granted.

You can verify that your role has the REPLICATION privilege by running the following query:

SELECT rolname, rolreplication
FROM pg_roles
WHERE rolname = '<role_name>';

A subscriber must be able to access the Neon database that is acting as a publisher. In Neon, no action is required unless you use Neon's IP Allow feature to limit IP addresses that can connect to Neon.

Important: When a subscriber connects to a Neon publisher, use a direct connection string, not a pooled one. Logical replication requires a persistent connection and is not compatible with connection poolers. Make sure the connection string you give the subscriber does not include the -pooler suffix in the hostname. See Connection pooling.

If you use Neon's IP Allow feature:

1. Determine the IP address or addresses of the subscriber.
2. In your Neon project, add the IPs to your IP Allow list, which you can find in your project's settings. For instructions, see Configure IP Allow.

When replicating data to Neon, you may need to allow connections from Neon on the publisher platform or service.

Neon uses 3 to 6 IP addresses per region for outbound communication, corresponding to each availability zone in the region. See NAT Gateway IP addresses for Neon's NAT gateway IP addresses. When configuring access, be sure to open access to all of the NAT gateway IP addresses for your Neon project's region.

Neon supports both pgoutput and wal2json replication output decoder plugins.

• pgoutput: This is the default logical replication output plugin for Postgres. Specifically, it's part of the Postgres built-in logical replication system, designed to read changes from the database's write-ahead log (WAL) and output them in a format suitable for logical replication.
• wal2json: This is also a logical replication output plugin for Postgres, but it differs from pgoutput in that it converts WAL data into JSON format. This makes it useful for integrating Postgres with systems and applications that work with JSON data. For usage information, see The wal2json plugin.

Some data services and platforms require dedicated replication slots. You can create a dedicated replication slot using the standard PostgreSQL syntax. As mentioned above, Neon supports both pgoutput and wal2json replication output decoder plugins.

SELECT pg_create_logical_replication_slot('my_replication_slot', 'pgoutput');

SELECT pg_create_logical_replication_slot('my_replication_slot', 'wal2json');

The max_wal_senders and max_replication_slots configuration parameter settings on Neon are set to 10.

max_wal_senders = 10
max_replication_slots = 10

• The max_wal_senders parameter defines the maximum number of concurrent WAL sender processes that are responsible for streaming WAL data to subscribers. In most cases, you should have one WAL sender process for each subscriber or replication slot to ensure efficient and consistent data replication.
• The max_replication_slots defines the maximum number of replication slots used to manage database replication connections. Each replication slot tracks changes in the publisher database to ensure that the connected subscriber stays up to date. You'll want a replication slot for each replication connection. For example, if you expect to have 10 separate subscribers replicating from your database, you would set max_replication_slots to 10 to accommodate each connection.

If you require different values for these parameters, please contact Neon support.

Each branch in a Neon project has its own Postgres instance, and a Postgres instance is a database cluster, capable of supporting multiple databases. If your use case requires replicating data between two databases in the same database cluster, i.e., on the same Neon project branch, the setup is slightly different than configuring replication between separate Postgres instances. As described in the official PostgreSQL CREATE SUBSCRIPTION Notes documentation:

Creating a subscription that connects to the same database cluster (for example, to replicate between databases in the same cluster or to replicate within the same database) will only succeed if the replication slot is not created as part of the same command. Otherwise, the `CREATE SUBSCRIPTION` call will hang. To make this work, create the replication slot separately (using the function `pg_create_logical_replication_slot` with the plugin name `pgoutput`) and create the subscription using the parameter `create_slot = false`. This is an implementation restriction that might be lifted in a future release.

For example, on the publisher database, you would create the publication and the replication slot, as shown:

CREATE PUBLICATION my_publication FOR TABLES <table1>, <table2>;
SELECT pg_create_logical_replication_slot('my_replication_slot', 'pgoutput');

Then, on the subscriber database, you would create a subscription that references the replication slot with the create_slot option set to false and slot_name set to the name of the slot you created. The connection_string should be the connection string for the Postgres role used to connect to the publisher database. This role must have the REPLICATION privilege. Any Postgres role create created via the Neon Console, CLI, or API is a member of the neon_superuser role, which has the REPLICATION privilege by default. You can find your Neon database connection details by clicking the Connect button in the Console nav to open the Connect to your branch modal. See Connect from any application. Be sure to select the correct role and database before copying the connection string.

CREATE SUBSCRIPTION my_subscription
    CONNECTION 'connection_string'
    PUBLICATION my_publication with (create_slot = false, slot_name = 'my_replication_slot');

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