[blnkfinance](https://github.com/blnkfinance) # Ship transaction workflowson an open-source ledger An immutable, double-entry ledger you run in production. Every workflow becomes a transaction you can trace, audit, and reconcile. Install Blnk Copy ``` $git clone https://github.com/blnkfinance/blnk && cd blnk && docker compose up ``` [Explore docs](https://docs.blnkfinance.com) ## Transaction details USD Amount Description ## Transaction workflows Add workflow Reset 200 OK TypeScript Go Python Java cURL Run Go back ``` const response = await blnk.Transactions.create({ precise_amount: 125034, precision: 100, currency: 'USD', source: '@WorldUSD', destination: '@MyBalance', reference: 'ref_f482a1b3-6c2d-4e89-a17b-3d5e8f2a1c94', description: 'Customer payment', skip_queue: true,}); ``` Running Trusted by developers in production: -  -  -  -  -  ## Built-in correctness and reliability - ### Double-entry accounting Every transaction has a source and a destination. Debits always equal credits, so the books cannot silently drift. | Amount | Source | Destination | | --- | --- | --- | | $100.00 | Ada | James | | $60.00 | James | @World | | $40.00 | @World | Ada | | User | Debit | Credit | | --- | --- | --- | | Ada | $0.00 | $0.00 | | James | $0.00 | $0.00 | | @World | $0.00 | $0.00 | - ### Immutable records Recorded transactions cannot be edited or deleted. History is only appended. | Amount | Status | | --- | --- | | $9,999.00 txn_8c21a4 | Applied | | $2,410.50 txn_3e07b1 | Applied | | £890.00 txn_91d4c8 | Applied | | $2,100.00 txn_a61e90 | Applied | | €1,180.00 txn_4d08b1 | Applied | | €3,420.10 txn_c3e572 | Applied | | $640.18 txn_18af06 | Applied | | £210.40 txn_e90c44 | Applied | - ### Reliable at scale Concurrent transactions are ordered and applied safely, preventing conflicting writes from corrupting balances under high traffic. James Carter USD $0.00 1 CR $50.00 Queued Applied 2 DR $20.00 Queued Applied 3 CR $40.00 Queued Applied 4 DR $10.00 Queued Applied 5 CR $30.00 Queued Applied 6 DR $20.00 Queued Applied 7 CR $50.00 Queued Applied 8 DR $30.00 Queued Applied 9 CR $20.00 Queued Applied 10 DR $10.00 Queued Applied ## Model multicurrency workflowswith precise money movement - ### Balances in any currency Store multiple currencies in the same ledger and organize balances in ledger folders. James Carter USD $1,250.34 Emily Brooks EUR €3,420.10 Michael Reed GBP £890.00 Sarah Bennett BTC 0.08421000 - ### Currency exchange workflows Model FX conversions and move value between currencies with a complete transaction audit trail. USD GBP FX Out USD 1,000.00 James Carter @Nostro-USD FX In GBP 790.00 @Nostro-GBP James Carter - ### Exact amounts, any asset Record BTC, ETH, and other digital assets down to their smallest supported unit. Balances Assets - 0.08421000 BTC $7,412.18 - 1.25084731 ETH $4,221.61 - 1,250.340000 USDC $1,250.34 - 18.420000000 SOL $3,184.26 - 2,410.500000 XRP $1,518.62 - 12,840.12000000 DOGE $2,054.42 - 4,180.250000 ADA $1,672.10 - 32.150000000 AVAX $1,157.40 ## Reserve funds with inflight. Release or clear only whenyour conditions are met. Commit Void JC James Carter | Balance | $ 1,250.00 | | --- | --- | | Inflight debit Amount waiting to be sent | $ 0.00 | $400.00 Inflight Applied Void 1. Fraud 2. KYC 3. Sanctions AO Ada Okonkwo | Balance | $ 0.00 | | --- | --- | | Inflight credit Amount waiting to be received | $ 0.00 | ## Integrate your ledger transactions withany stack, provider or payment rail - ### Your ledger is the source of truth Put it in front of any payment provider or rail and integrate the third parties you already use.  %20--%3e%3csvg%20version='1.1'%20id='Layer_1'%20xmlns='http://www.w3.org/2000/svg'%20xmlns:xlink='http://www.w3.org/1999/xlink'%20x='0px'%20y='0px'%20style='enable-background:new%200%200%20468%20222.5;'%20xml:space='preserve'%20viewBox='54%2036%20360.02%20149.84'%3e%3cstyle%20type='text/css'%3e%20.st0{fill-rule:evenodd;clip-rule:evenodd;fill:%23635BFF;}%20%3c/style%3e%3cg%3e%3cpath%20class='st0'%20d='M414,113.4c0-25.6-12.4-45.8-36.1-45.8c-23.8,0-38.2,20.2-38.2,45.6c0,30.1,17,45.3,41.4,45.3%20c11.9,0,20.9-2.7,27.7-6.5v-20c-6.8,3.4-14.6,5.5-24.5,5.5c-9.7,0-18.3-3.4-19.4-15.2h48.9C413.8,121,414,115.8,414,113.4z%20M364.6,103.9c0-11.3,6.9-16,13.2-16c6.1,0,12.6,4.7,12.6,16H364.6z'%3e%3c/path%3e%3cpath%20class='st0'%20d='M301.1,67.6c-9.8,0-16.1,4.6-19.6,7.8l-1.3-6.2h-22v116.6l25-5.3l0.1-28.3c3.6,2.6,8.9,6.3,17.7,6.3%20c17.9,0,34.2-14.4,34.2-46.1C335.1,83.4,318.6,67.6,301.1,67.6z%20M295.1,136.5c-5.9,0-9.4-2.1-11.8-4.7l-0.1-37.1%20c2.6-2.9,6.2-4.9,11.9-4.9c9.1,0,15.4,10.2,15.4,23.3C310.5,126.5,304.3,136.5,295.1,136.5z'%3e%3c/path%3e%3cpolygon%20class='st0'%20points='223.8,61.7%20248.9,56.3%20248.9,36%20223.8,41.3%20'%3e%3c/polygon%3e%3crect%20x='223.8'%20y='69.3'%20class='st0'%20width='25.1'%20height='87.5'%3e%3c/rect%3e%3cpath%20class='st0'%20d='M196.9,76.7l-1.6-7.4h-21.6v87.5h25V97.5c5.9-7.7,15.9-6.3,19-5.2v-23C214.5,68.1,202.8,65.9,196.9,76.7z'%3e%3c/path%3e%3cpath%20class='st0'%20d='M146.9,47.6l-24.4,5.2l-0.1,80.1c0,14.8,11.1,25.7,25.9,25.7c8.2,0,14.2-1.5,17.5-3.3V135%20c-3.2,1.3-19,5.9-19-8.9V90.6h19V69.3h-19L146.9,47.6z'%3e%3c/path%3e%3cpath%20class='st0'%20d='M79.3,94.7c0-3.9,3.2-5.4,8.5-5.4c7.6,0,17.2,2.3,24.8,6.4V72.2c-8.3-3.3-16.5-4.6-24.8-4.6%20C67.5,67.6,54,78.2,54,95.9c0,27.6,38,23.2,38,35.1c0,4.6-4,6.1-9.6,6.1c-8.3,0-18.9-3.4-27.3-8v23.8c9.3,4,18.7,5.7,27.3,5.7%20c20.8,0,35.1-10.3,35.1-28.2C117.4,100.6,79.3,105.9,79.3,94.7z'%3e%3c/path%3e%3c/g%3e%3c/svg%3e)   %20--%3e%3c!DOCTYPE%20svg%20PUBLIC%20'-//W3C//DTD%20SVG%201.1//EN'%20'http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd'%3e%3csvg%20version='1.1'%20id='Layer_1'%20xmlns='http://www.w3.org/2000/svg'%20xmlns:xlink='http://www.w3.org/1999/xlink'%20x='0px'%20y='0px'%20viewBox='0%200%20101.6%2032.9'%20style='enable-background:new%200%200%20101.6%2032.9;'%20xml:space='preserve'%3e%3cstyle%20type='text/css'%3e%20.st0{fill:%2335B454;}%20%3c/style%3e%3cg%3e%3cg%3e%3cpath%20class='st0'%20d='M14.3,7.5H0.3V12l9.2,0c0.6,0,1,0.5,1,1v7.9h-2c-0.6,0-1-0.5-1-1v-5.7H3.6c-2,0-3.6,1.6-3.6,3.6v4%20c0,2,1.6,3.6,3.6,3.6h14.3V11.1C17.9,9.1,16.3,7.5,14.3,7.5z'/%3e%3c/g%3e%3cg%3e%3cpath%20class='st0'%20d='M31.4,20.9h-2c-0.6,0-1-0.5-1-1V7.5h-3.9c-2,0-3.6,1.6-3.6,3.6v10.7c0,2,1.6,3.6,3.6,3.6h14.3V0h-7.5%20L31.4,20.9z'/%3e%3c/g%3e%3cg%3e%3cpath%20class='st0'%20d='M52.3,20.9h-2c-0.6,0-1-0.5-1-1V7.5h-7.5v14.3c0,2,1.6,3.6,3.6,3.6h6.9v2.2H42.1v5.2h14.1%20c2,0,3.6-1.6,3.6-3.6V7.5h-7.5V20.9z'/%3e%3c/g%3e%3cg%3e%3cpath%20class='st0'%20d='M77.1,7.5H62.7v14.3c0,2,1.6,3.6,3.6,3.6h14.1v-4.5h-9.2c-0.6,0-1-0.5-1-1V12h2c0.6,0,1,0.5,1,1v5.7h3.9%20c2,0,3.6-1.6,3.6-3.6v-4C80.7,9.1,79.1,7.5,77.1,7.5z'/%3e%3c/g%3e%3cg%3e%3cpath%20class='st0'%20d='M98,7.5H83.7v17.9h7.5V12h2c0.6,0,1,0.5,1,1v12.4h7.5V11.1C101.6,9.1,100,7.5,98,7.5z'/%3e%3c/g%3e%3c/g%3e%3c/svg%3e)             - ### Post from the stack you already have Use our REST API and SDKs with the languages and infrastructure you already use. TypeScript cURL Go Python Java ``` const response = await blnk.Transactions.create({ precise_amount: 123012, precision: 100, currency: 'USD', source: '@WorldUSD', destination: '@MyBalance', reference: 'ref_f482a1b3-6c2d-4e89-a17b-3d5e8f2a1c94', description: 'Wallet top-up for Ada Okonkwo', inflight: true, allow_overdraft: true, skip_queue: true,});if (checksComplete) { await blnk.Transactions.updateStatus( response.data.transaction_id, { status: 'commit' }, );} else { await blnk.Transactions.updateStatus( response.data.transaction_id, { status: 'void' }, );} ``` ``` curl -X POST "http://YOUR_BLNK_INSTANCE_URL/transactions" \ -H "X-blnk-key: $BLNK_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "precise_amount": 123012, "precision": 100, "currency": "USD", "source": "@WorldUSD", "destination": "@MyBalance", "reference": "ref_f482a1b3-6c2d-4e89-a17b-3d5e8f2a1c94", "description": "Wallet top-up for Ada Okonkwo", "inflight": true, "allow_overdraft": true, "skip_queue": true }'if [ "$CHECKS_COMPLETE" = true ]; then curl -X PUT "http://YOUR_BLNK_INSTANCE_URL/transactions/inflight/$TRANSACTION_ID" \ -H "X-blnk-key: $BLNK_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "status": "commit" }'else curl -X PUT "http://YOUR_BLNK_INSTANCE_URL/transactions/inflight/$TRANSACTION_ID" \ -H "X-blnk-key: $BLNK_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "status": "void" }'fi ``` ``` transaction, resp, err := client.Transaction.Create( blnkgo.CreateTransactionRequest{ ParentTransaction: blnkgo.ParentTransaction{ PreciseAmount: big.NewInt(123012), Precision: 100, Currency: "USD", Source: "@WorldUSD", Destination: "@MyBalance", Reference: "ref_f482a1b3-6c2d-4e89-a17b-3d5e8f2a1c94", Description: "Wallet top-up for Ada Okonkwo", }, Inflight: true, AllowOverdraft: true, SkipQueue: true, },)if checksComplete { transaction, resp, err = client.Transaction.Update( transaction.TransactionID, blnkgo.UpdateStatus{ Status: blnkgo.InflightStatusCommit }, )} else { transaction, resp, err = client.Transaction.Update( transaction.TransactionID, blnkgo.UpdateStatus{ Status: blnkgo.InflightStatusVoid }, )} ``` ``` response = blnk.transactions.create({ "precise_amount": 123012, "precision": 100, "currency": "USD", "source": "@WorldUSD", "destination": "@MyBalance", "reference": "ref_f482a1b3-6c2d-4e89-a17b-3d5e8f2a1c94", "description": "Wallet top-up for Ada Okonkwo", "inflight": True, "allow_overdraft": True, "skip_queue": True,})if checks_complete: blnk.transactions.update_status( response["transaction_id"], {"status": "commit"}, )else: blnk.transactions.update_status( response["transaction_id"], {"status": "void"}, ) ``` ``` ApiResponse response = blnk.transactions().create( CreateTransactions.create() .preciseAmount(123012) .precision(100) .currency("USD") .source("@WorldUSD") .destination("@MyBalance") .reference("ref_f482a1b3-6c2d-4e89-a17b-3d5e8f2a1c94") .description("Wallet top-up for Ada Okonkwo") .inflight(true) .allowOverdraft(true) .skipQueue(true));if (checksComplete) { blnk.transactions().updateStatus( response.data().get("transaction_id").asText(), UpdateTransactionStatus.create().status("commit"));} else { blnk.transactions().updateStatus( response.data().get("transaction_id").asText(), UpdateTransactionStatus.create().status("void"));} ``` - ### Automate reconciliation Match ledger transactions against external records and quickly identify drifts across payment rails. | Amount | Status | | --- | --- | | $1,250.34 ref_7f3a2c | Reconciled No match | | $2,410.50 ref_9b18e4 | Reconciled No match | | £890.00 ref_2c41d8 | Reconciled No match | | $2,100.00 ref_a61e90 | Reconciled No match | | €1,180.00 ref_4d08b1 | Reconciled No match | | €3,420.10 ref_c3e572 | Reconciled No match | | $640.18 ref_18af06 | Reconciled No match | | £210.40 ref_e90c44 | Reconciled No match | Stories ## Hundreds of engineers sleep well at night with Blnk powering their product. [Read more stories](https://blnkfinance.com/customers) Customer testimonials - The support from the team was incredible. They not only guided us through their product but also helped us implement it within our system. — Sajith Caldera, CEO, Bitnomi - We are very convinced that you are the right team. We believe you can shorten our development time from a year to four months. — Mario León, CEO, Morna Tech - Given the fact that Blnk is open-source, with support for a managed Cloud dashboard, you have solved 70% of our engineering problems. — Mohammed Al-Ameen, Head of Engineering, Digitvant - Blnk is the best solution that I have found until now. The other choices are a bit too complex to use and do too much. Blnk does the job that a ledger needs to do without complexity. — Antonio, CTO, BR Tokens - I’ve done a bit of research with some other products personally… and so far, we both think that yours stood out ahead of the other open-source competition. — Fahad Khawaja, Senior Engineer, Oraan - We know we won’t get everything right the first time. But with Blnk, we are confident that we can keep iterating until we do. — Patrick McEvoy, CTO, Oraan - The personal touch is what makes you better/different from your competitors. — Prerak Motwany, Co-founder, Bitnomi - I’m not very good with accounting, but the docs were easy to understand and helped us get started right away. — Kevis Rondon, CTO, Morna Tech - Integration was seamless, and the fact that it’s open-source adds flexibility. On top of that, Blnk is incredibly fast, making it a solid choice for high-performance financial systems. — Toni Akinmolayan, Senior Engineer, Yousend - It’s the best and most comprehensive solution that I have found. — Awale Jamac, Co-founder, Onbilia > The support from the team was incredible. They not only guided us through their product but also helped us implement it within our system. Sajith Caldera CEO, Bitnomi > We are very convinced that you are the right team. We believe you can shorten our development time from a year to four months. Mario León CEO, Morna Tech > Given the fact that Blnk is open-source, with support for a managed Cloud dashboard, you have solved 70% of our engineering problems. Mohammed Al-Ameen Head of Engineering, Digitvant > Blnk is the best solution that I have found until now. The other choices are a bit too complex to use and do too much. Blnk does the job that a ledger needs to do without complexity. Antonio CTO, BR Tokens > I’ve done a bit of research with some other products personally… and so far, we both think that yours stood out ahead of the other open-source competition. Fahad Khawaja Senior Engineer, Oraan > The support from the team was incredible. They not only guided us through their product but also helped us implement it within our system. Sajith Caldera CEO, Bitnomi > We are very convinced that you are the right team. We believe you can shorten our development time from a year to four months. Mario León CEO, Morna Tech > Given the fact that Blnk is open-source, with support for a managed Cloud dashboard, you have solved 70% of our engineering problems. Mohammed Al-Ameen Head of Engineering, Digitvant > Blnk is the best solution that I have found until now. The other choices are a bit too complex to use and do too much. Blnk does the job that a ledger needs to do without complexity. Antonio CTO, BR Tokens > I’ve done a bit of research with some other products personally… and so far, we both think that yours stood out ahead of the other open-source competition. Fahad Khawaja Senior Engineer, Oraan > We know we won’t get everything right the first time. But with Blnk, we are confident that we can keep iterating until we do. Patrick McEvoy CTO, Oraan > The personal touch is what makes you better/different from your competitors. Prerak Motwany Co-founder, Bitnomi > I’m not very good with accounting, but the docs were easy to understand and helped us get started right away. Kevis Rondon CTO, Morna Tech > Integration was seamless, and the fact that it’s open-source adds flexibility. On top of that, Blnk is incredibly fast, making it a solid choice for high-performance financial systems. Toni Akinmolayan Senior Engineer, Yousend > It’s the best and most comprehensive solution that I have found. Awale Jamac Co-founder, Onbilia > We know we won’t get everything right the first time. But with Blnk, we are confident that we can keep iterating until we do. Patrick McEvoy CTO, Oraan > The personal touch is what makes you better/different from your competitors. Prerak Motwany Co-founder, Bitnomi > I’m not very good with accounting, but the docs were easy to understand and helped us get started right away. Kevis Rondon CTO, Morna Tech > Integration was seamless, and the fact that it’s open-source adds flexibility. On top of that, Blnk is incredibly fast, making it a solid choice for high-performance financial systems. Toni Akinmolayan Senior Engineer, Yousend > It’s the best and most comprehensive solution that I have found. Awale Jamac Co-founder, Onbilia -  Public Grid ### How Public Grid went from bare Postgres to a production-grade ledger [Read Public Grid's story](https://blnkfinance.com/customers/public-grid) -  Morna Tech ### How Morna Tech cut a year of development to 6 months with Blnk [Read Morna Tech's story](https://blnkfinance.com/customers/morna-tech) -  Yousend ### How Yousend shipped cross-border payments with Blnk Finance [Read Yousend's story](https://blnkfinance.com/customers/yousend) -  Tecnología Financiera ### How Tecnología Financiera uses its licenses and Blnk to power Venezuela’s fintechs [Read Tecnología Financiera's story](https://blnkfinance.com/customers/tecnologia-financiera) Security ## Open-source ledger infrastructure you can trust Blnk is ISO/IEC 27001-certified and GDPR-compliant. Built with security features and best practices auditors ask for. [How we handle security](https://blnkfinance.com/security)   ### ISO/IEC 27001 and GDPR Blnk’s ISMS is certified to ISO/IEC 27001. Personal data is processed under GDPR. ### Encryption in transit and at rest Sensitive data at rest is encrypted with AES-256-GCM. Data in transit uses TLS 1.2 or higher. ### Role-based access control Give every team member the access they need, and nothing more. Granular roles keep sensitive ledger operations restricted while making audits and reviews straightforward. ### Built for security reviews We support vendor and security reviews with clear policies around access control, information security, incident response, and business continuity. ## FAQs Have other questions? Email us at [support@blnkfinance.com](mailto:support@blnkfinance.com). What is Blnk Core? Blnk Core is an open-source ledger for transaction workflows. You post the movement. Core keeps the balances, conversions, rails, and matches around it. What can I build with Blnk Core? You can build products that need to track money and balances, including wallets, lending products, marketplaces, savings, insurance, trading, and payment applications. Is Blnk a payment provider or payment rail? No. Blnk is the ledger. You continue to use providers and rails such as Stripe, Unit, bank transfers, or card networks to move money. Blnk records those movements and keeps your financial state in one place. Can Blnk work alongside my existing ledger? Yes. You can run Blnk as a shadow ledger alongside your existing system. This gives you a way to validate balances and transaction records before making it the primary ledger. How does Blnk keep balances accurate? Every transaction has a source and a destination. Debits always equal credits, so the books cannot silently drift. Concurrent transactions are applied in order, and configurable precision prevents unwanted rounding. How do I integrate Blnk with my application? Blnk provides REST APIs that you can use from any language or framework. You can integrate it into your existing application stack without adopting a specific programming language or infrastructure. Can I try Blnk before using it in production? Yes. You can create a [Blnk Cloud sandbox](https://cloud.blnkfinance.com/auth/sign-up) , create balances, post transactions, connect a payment rail, and test your workflows before moving to production. Is Blnk Core free? The open-source Core engine is free to run. Paid offerings are available for teams that need managed infrastructure, a back office, support, production guarantees, or commercial licensing. Can Blnk handle production workloads? Yes. Blnk is designed to handle production financial workloads, from startup applications to systems processing high transaction volumes. Your deployment architecture and infrastructure determine the capacity of a specific installation.