One API for Many Billers

Challenge

Every biller spoke a different protocol — REST, SOAP or file exchange — with its own reference formats, settlement rules and security requirements. Partners needed one consistent way to make payments, payouts, refunds and top-ups. Cash-in and cash-out at agent locations had to be impossible to brute-force.

Approach

• Normalize the model, not just the transport. One documented API exposes payments, payouts, refunds, recharges, fees, commissions and exchange rates consistently, regardless of which biller sits behind it.
• Meet each partner's security bar. Mutual TLS where required, and signed, encrypted messages (JWS/JWE) for partners that demand message-level security.
• Design cash operations to resist guessing. One-time codes are stored only as hashes, compared in constant time, expire, and are bound to the account, biller and transaction type. Attempts are limited, with time-boxed lockouts.
• Reject duplicates at the door. Repeated payment and payout requests are detected per client, biller and account.

Implementation

• Partner endpoints for payments, payouts, refunds, top-ups, fees, commissions, promotions, accounts, billers and webhooks.
• Biller adapters for REST and SOAP services, including a WS-Security SOAP integration and an mTLS client.
• A cash-in / cash-out service with code generation, account validation, lockouts, scheduled expiry and partner webhook notifications.
• Event publishing to Kafka, caching, and background processing for biller master files.

Outcome

Partners integrate once and reach many billers. Agent cash operations are protected by single-use, expiring codes and bounded attempts.

Technical perspective

Each integration brings its own protocol, cryptography and failure semantics. Moving money means idempotency and auditability have to hold even when a downstream biller times out halfway through a request.