Getting Started with Blnk

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Overview

This is your guide to getting started with Blnk, pronounced as /blank/. If you are new to Blnk or open-source fintech developer tools, this is where you should start.

Here is your start kit: ✨

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What is Blnk?

Blnk offers an open-source financial ledger database for building and scaling fintech products. With Blnk, you can:

• Accurately record transactions in your system.
• Correctly manage complex flow of funds and transaction data.
• Reliably manage the size of your transactions as your product scales.

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1. Install Blnk on your machine

To install Blnk, make sure you have Docker and Compose installed and running on your machine.

To get started with Blnk, first clone the repository into your machine:

git clone https://github.com/blnkfinance/blnk && cd blnk

Next, create a configuration file, blnk.json:

touch blnk.json

Then copy and save the following configuration:

{
  "project_name": "Blnk",
  "data_source": {
    "dns": "postgres://postgres:password@postgres:5432/blnk?sslmode=disable"
  },
  "redis": {
    "dns": "redis:6379"
  },
  "server": {
    "port": "5001"
  },
  "queue": {
    "monitoring_port": "5004"
  }
}

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2. Launch Blnk

Start your Blnk server with Docker compose:

docker compose up

If successful, you should be able to access your server on the following URL:

http://localhost:5001

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3. Create your first ledger

Everything in Blnk begins with a ledger. Ledgers are used to group and manage how you arrange your ledger balances in our application.

When you install Blnk, an internal ledger called the General Ledger is created for you. This is a ledger meant for grouping all of the balances directly owned by your organization, e.g., Revenue, Fees, etc.

However, to create, store and represent balances for accounts/wallets owned by the users in your application, it is required to create ledgers to group them in.

To create a ledger, call the create-ledger endpoint:

POST http://YOUR_BLNK_INSTANCE_URL/ledgers

With the following request body:

{
    "name": "Customer Savings Account",
    "meta_data": {
        "project_owner": "YOUR_APP_NAME"
    }
}

{
    "ledger_id": "ldg_073f7ffe-9dfd-42ce-aa50-d1dca1788adc",
    "name": "Customer Savings Account",
    "created_at": "2024-12-21T01:36:46.997063436Z",
    "meta_data":{
        "project_owner": "YOUR_APP_NAME"
    }
}

Next, you can view a list of all your ledgers:

blnk ledgers list

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4. Create your first balance

Ledger balances (or balances for short) are used to represent store of value in a fintech application, e.g., wallet, crypto, account, card balance, etc. They represent the source or destination of a transaction record.

To create a balance, call the create-balance endpoint:

POST http://YOUR_BLNK_INSTANCE_URL/balances

With the following request body:

{
    "ledger_id": "ldg_073f7ffe-9dfd-42ce-aa50-d1dca1788adc",
    "currency": "USD",
    "meta_data": {
        "first_name": "Alice",
        "last_name": "Hart",
        "account_number": "1234567890"
    }
}

{
    "balance_id": "bln_0be360ca-86fe-457d-be43-daa3f966d8f0",
    "balance": 0,
    "version": 0,
    "inflight_balance": 0,
    "credit_balance": 0,
    "inflight_credit_balance": 0,
    "debit_balance": 0,
    "inflight_debit_balance": 0,
    "precision": 0,
    "ledger_id": "ldg_073f7ffe-9dfd-42ce-aa50-d1dca1788adc",
    "identity_id": "",
    "indicator": "",
    "currency": "USD",
    "created_at": "2024-02-20T05:33:01.311600208Z",
    "meta_data": {
        "first_name": "Alice",
        "last_name": "Hart",
        "account_number": "1234567890"
    }
}

Next, to view a list of all your balances:

blnk balances list

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5. Record your first transaction

Transactions represent all financial activities happening in your application. Blnk uses the double entry principle to record transactions, i.e., to successfully record a transaction, there must be a source and a destination.

In the code example below, we’ll fund our balance created above with a starting amount.

To record a transaction, call the record-transaction endpoint:

POST http://YOUR_BLNK_INSTANCE_URL/transactions

With the following request body:

{
    "amount": 750,
    "reference": "ref_001adcfgf",
    "currency": "USD",
    "precision": 100,
    "source": "@FundingPool",
    "destination": "bln_ebcd230f-6265-4d4a-a4ca-45974c47f746",
    "description": "Fund with starting balance amount",
    "allow_overdraft": true,
    "meta_data": {
      "sender_name": "John Doe",
      "sender_account": "00000000000"
    }
}

{
    "id": "txn_6164573b-6cc8-45a4-ad2e-7b4ba6a60f7d",
    "source": "@FundingPool",
    "destination": "bln_ebcd230f-6265-4d4a-a4ca-45974c47f746",
    "reference": "ref_001adcfgf",
    "amount": 750,
    "precision": 100,
    "precise_amount": 75000,
    "currency": "USD",
    "description": "Fund with starting balance amount",
    "allow_overdraft": true,
    "status": "QUEUED",
    "created_at": "2024-12-21T01:36:46.997063436Z",
    "meta_data": {
      "sender_name": "John Doe",
      "sender_account": "00000000000"
    }
}

Next, you can view a list of all transactions in your ledger:

blnk transactions list

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Use cases

Here’s some of what you can build with Blnk:

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Need help?

We are very happy to help you make the most of Blnk, regardless of whether it is your first time or you are switching from another tool.

To ask questions or discuss issues, please contact us or join our Discord community.