Case study
Ajo
Digital savings circles with Naira wallets, a double-entry ledger, Paystack funding, and automated payout rounds.
- Role
- Full-Stack Developer
- Year
- 2026
- Status
- Live
- Stack
- TypeScript · PostgreSQL · Paystack
Overview
Ajo brings the familiar rotating savings circle online: members fund individual wallets, contribute on a set schedule, and receive the full pot when it is their turn. The product keeps every movement traceable without asking one member to hold the group's money.
What it does
- 01
Naira wallets with card and bank-transfer top-ups through Paystack
- 02
Double-entry ledger with balances derived from immutable entries
- 03
Scheduled contribution collection and rotating payout rounds
- 04
Shareable circle invites with membership and schedule visibility
- 05
Idempotent payment and ledger writes to prevent duplicate charges
- 06
Transparent missed-payment records for every circle member
The hard part
Money movement needs to remain correct when a payment is retried, a webhook is delivered twice, or a scheduled round runs more than once. Idempotency keys and database transactions ensure each movement is settled exactly once or not at all.
What it taught me
For a financial product, the ledger is the source of truth. Deriving balances from matching debit and credit entries makes both the system and its audit trail easier to trust.