Case study 09
Microfinance Core Banking System
A core banking system for NGOs that run microfinance programmes. It covers group lending and savings products from loan disbursement through repayment schedules and field-agent collection, and posts every transaction to a double-entry ledger that reconciles. It runs in 3 organizations across 20 branches, with microcredit portfolio management, HR/payroll and MIS/AIS reporting alongside.
No public site or source code. The architecture and the decisions behind it are described below.
- Founding Engineer & Tech Lead
- Enterprise
- FinTech
- Core Banking, Microfinance, Double-entry Accounting, Multi-tenancy
- Next.js
- NestJS
- PostgreSQL
- Redis
- BullMQ
- TypeORM
What Microfinance Core Banking does
- Group lending and savings products
- Loan disbursement, repayment schedules and field-agent collection
- Double-entry ledger with transaction posting and reconciliation
- Microcredit portfolio management
- HR and payroll
- MIS and AIS reporting
The problem
Microfinance NGOs run on small loans to groups of borrowers, collected weekly by field agents. Every taka has to be accounted for, across many branches, under audit. Spreadsheets break down quickly at that scale.
Approach
Every operation, whether a disbursement, a collection or an interest accrual, becomes a balanced journal posting in one double-entry ledger. Branch, product and borrower views are projections of that ledger, so reports reconcile by construction. Repayment schedules and accruals run as scheduled background jobs rather than request-time calculations.
Key decisions
- D1
One ledger, many views
Portfolio, savings and branch reports are queries over posted journal lines, not separately maintained totals, so they can't drift apart.
- D2
Tenant per organisation
Each NGO is a tenant with its own branches, products and chart of accounts, so one deployment serves several organisations.
- D3
Jobs for time-based money
Interest, schedules and overdue flags are computed by queued jobs with retries, keeping the API responsive at month end.
Highlights
- Covers group lending, savings products, loan disbursement, repayment scheduling and field-agent collection, with training and technical support for deployments.
- Engineered the double-entry accounting ledger with transaction posting and reconciliation, alongside microcredit portfolio management, HR/payroll and MIS/AIS reporting.
My contributions
- Ran requirements analysis with the microfinance operations it had to serve
- Architected the system and chose the tech stack
- Designed the database, including the multi-tenant model and the double-entry ledger
- Built the foundation across frontend, backend and database so other engineers and teams could build on it without friction
- Kept engineering hands-on while leading teams of 5–7 mid-level and junior engineers on the project