Configure your Rell module

This lesson walks you through setting the Vector Database Extension's dimensionality in chromia.yml and getting the file ready for a Chromia testnet deployment.

Open the rell/ folder

If your terminal is still in the python/ folder from the last step, return to the project root:

cd ..

Then change into the folder that holds the Rell backend:

cd rell

Set the correct embedding dimensions

In chromia.yml, locate this section:

blockchains:  vector_demo:  # Update this to a unique name before deployment    module: vector_interface    config:      gtx:        modules:          - "net.postchain.gtx.extensions.vectordb.VectorDbGTXModule"      vector_db_extension:        dimensions: 768  # Match your selected embedding model

Change the dimensions: value so it fits the embedding model you picked earlier:

Set a unique chain name

Generate a deployment key

The deployment transaction must be signed with a deployment key. If you don't have one yet, create it with:

chr keygen --key-id="vector_db_demo_key"

The command writes a fresh key pair to your local .chromia directory.

Your private key is stored here:

~/.chromia/vector_db_demo_key

Open the file, copy the entire hex-encoded private key, and set it as the PRIV_KEY value in the .env file inside the python/ folder:

PRIV_KEY=<your-private-key>

You need this key to sign the transactions that upload or query vectors on-chain.

Lease a container on testnet

Deployment requires a leased container with Vector Database Extension support.

Use this guide to lease one and get its container ID:

Get a container on Chromia testnet

With the container leased, add its ID to chromia.yml like this:

deployments:  testnet:    brid: x"6F1B061C633A992BF195850BF5AA1B6F887AEE01BB3F51251C230930FB792A92"    url: https://node0.testnet.chromia.com:7740    container: <your-container-id>    # After deployment, insert the generated `chains:` section here

Don't change brid or url; they already reference the testnet Directory Chain and node0.

What’s next?

Your chromia.yml now has the container ID, the right embedding dimensions, and a unique chain name, and you have a deployment key. That's everything required to deploy the Rell module, which the next lesson covers.