In this quickstart, you’ll create a real-time data pipeline that streams changes from a Postgres database to a NATS subject. You’ll:

  • Boot Sequin
  • Connect to a sample playground database
  • Configure a NATS subject to receive database changes
  • See your changes flow in real-time

By the end, you’ll have hands-on experience setting up Postgres change data capture (CDC) with Sequin. This same pattern can be used to setup your own Postgres CDC pipeline with NATS.

Boot NATS

If you don’t already have NATS running, start NATS with Docker:

docker run --name nats -p 4222:4222 -d nats:latest

If you’re using another NATS instance, ensure you have the connection details ready.

Run Sequin

The easiest way to get started with Sequin is with our Docker Compose file. This file starts a Postgres database, Redis instance, and Sequin server.

1

Create directory and start services

  1. Download sequin-docker-compose.zip.
  2. Unzip the file.
  3. Navigate to the unzipped directory and start the services:
cd sequin-docker-compose && docker compose up -d
2

Verify services are running

Check that Sequin is running using docker ps:

docker ps

You should see output like the following:

CONTAINER ID   IMAGE                                 STATUS          PORTS                                       NAMES
abc123def456   sequinstream/sequin:latest           Up 10 seconds    0.0.0.0:7376->7376/tcp                     sequin
def456ghi789   redis:7.0                            Up 10 seconds    0.0.0.0:6379->6379/tcp                     sequin-redis
ghi789jkl012   postgres:15                          Up 10 seconds    0.0.0.0:5432->5432/tcp                     sequin-postgres

All three containers should be up and running (status: Up).

Login

The Docker Compose file automatically configures Sequin with an admin user and a playground database.

Let’s log in to the Sequin web console:

1

Open the web console

After starting the Docker Compose services, open the Sequin web console at http://localhost:7376:

2

Login with default credentials

Use the following default credentials to login:

  • Email:
admin@sequinstream.com
  • Password:
sequinpassword!

View the playground database

To get you started quickly, Sequin’s Docker Compose file creates a logical database called sequin_playground with a sample dataset in the public.products table.

Let’s take a look:

1

Navigate to Databases

In the Sequin web console, click Databases in the sidebar.

2

Select playground database

Click on the pre-configured sequin-playground database:

The database “Health” should be green.

3

View contents of the products table

Let’s get a sense of what’s in the products table. Run the following command:

docker exec -i sequin-sequin_postgres-1 \
  psql -U postgres -d sequin_playground -c \
  "select id, name, price from products;"

This command connects to the running Postgres container and runs a psql command.

You should see a list of the rows in the products table:

  id |         name          | price 
----+-----------------------+-------
  1 | Avocados (3 pack)     |  5.99
  2 | Flank Steak (1 lb)    |  8.99
  3 | Salmon Fillet (12 oz) | 14.99
  4 | Baby Spinach (16 oz)  |  4.99
  5 | Sourdough Bread       |  6.99
  6 | Blueberries (6 oz)    |  3.99
(6 rows)

We’ll make modifications to this table in a bit.

Subscribe to NATS

Before creating the sink, let’s set up a subscriber to watch for messages. You can use the NATS CLI container:

docker run --rm -it --network host natsio/nats-box:latest
nats sub "sequin.>"

Keep this terminal window open - you’ll see messages start flowing once we create the sink.

Create a NATS Sink

With the playground database connected, you can create a sink. This sink will send changes to the products table to your NATS subject:

1

Navigate to Sinks

Click “Sinks” in the sidebar navigation, then click “Create Sink”.

2

Select sink type

Select “NATS” as the sink type and click “Continue”.

3

Note Source configuration

In the “Source” card, note that the sequin-playground database and products table are pre-selected. Leave these defaults:

4

Setup a backfill

In the “Initial backfill” card, click the toggle to enable an initial backfill. You can leave the default start position, which will backfill all existing rows in the products table:

5

Configure "NATS Configuration"

In the “NATS Configuration” card, enter your NATS connection details:

  • Host: If running NATS and Sequin locally with Docker, use host.docker.internal
  • Port: The port NATS is listening on (default: 4222)
6

Test the connection

At the bottom of the form, click the “Test Connection” button. If you provided proper credentials, it should succeed.

Sequin can connect to your NATS server.

7

Create the sink

You can leave the rest of the defaults. As configured, the NATS subject will first receive a backfill of all rows currently in the products table. Then, it will receive all changes to the products table in real-time.

Click “Create Sink” to finish setting up your NATS sink.

See changes flow to your NATS subject

On the new sink’s overview page, you should see the “Health” status turn green, indicating data is flowing to your NATS subject.

Let’s confirm messages are flowing:

1

Messages tab

Click the “Messages” tab. You’ll see a list of the recently delivered messages:

Sequin indicates it backfilled the products table to your NATS subject.

2

Check your NATS subscription

Return to the terminal where you started the NATS subscription earlier. You should see the messages that were sent from Sequin:

These are read events from the initial backfill of the products table.

Messages are flowing from Sequin to your NATS subject.

3

Make some changes

Let’s make some changes to the products table and see them flow to your subject.

In your terminal, run the following command to insert a new row into the products table:

docker exec -i sequin-sequin_postgres-1 \
  psql -U postgres -d sequin_playground -c \
  "insert into products (name, price) values ('Organic Honey (16 oz)', 12.99);"

In your NATS subscription terminal, you should see a message corresponding to the inserted row.

Feel free to try other changes:

Each change will appear in your NATS subject within a few seconds.

Great work!

You’ve successfully:

  • Set up a complete Postgres change data capture pipeline
  • Loaded existing data through a backfill
  • Made changes to the products table
  • Verified changes are flowing to your NATS subject

​
Ready to stream

Now you’re ready to connect your own database to Sequin and start streaming changes:

Guide: Connect Postgres

Connect your Postgres database to Sequin.

Guide: Setting up a NATS sink

Setup a NATS sink to send changes to your subject.

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