Fintech · Food-service

Complete payments stack running on SmartPOS

Onboarding, payouts, split, and payment methods integrated on the terminal — embedded into the app of a B2B retail and food-service SaaS.

Context

When the SaaS becomes a fintech

A B2B SaaS for restaurant and retail management reached the point where the merchants' biggest pain was no longer operating the point of sale, but payments: opening an acquirer account, getting the terminal approved, handling multiple statements, and then reconciling everything against the revenue recorded in their own management system.

The obvious solution was to embed payments inside the app already running on the merchant's SmartPOS. A single onboarding point, a single checkout flow, and automatic reconciliation — and along the way, the company would capture margin on the transactional operation instead of handing it all over to the acquirer.

The client's team needed senior reinforcement in fintech, with real experience in sub-acquiring, PCI, and running code on Android SmartPOS hardware. The squad embedded with them and built the transactional stack from zero to go-live.

Challenge

What had to be solved

End-to-end PCI-DSS certification across capture and storage of card data
Sub-acquiring operations: KYC, settlement, payouts, and split between acquirer, marketplace, and merchant
Automated reconciliation D+0 (Pix) and D+30 (credit), reconciled against the acquirer's settlement
Simultaneous support for instant Pix, Apple Pay, Google Pay, and EMV credit via tap or insert
End-to-end latency below 500ms on the SmartPOS terminal, even on unstable mobile networks
Real-time antifraud combining a rules layer and an ML model for marginal decisions

Approach

How the team tackled it

Squad embedded with the client team, working in the same repository from day one
Event-driven architecture on Kafka, separating capture, authorization, settlement, and reconciliation
Integration with the payment gateway and the acquirer via native APIs
AWS KMS for sensitive data tokenization and automatic key rotation
Antifraud layer combining rules written by the risk team and an ML model trained on proprietary data
OTA deploys directly to the APK running on SmartPOS, with safe fleet-based rollback

Result

Headline milestone

Transactional operation in production 24/7

Complete payments stack running on merchants' SmartPOS — onboarding, capture, split, and reconciliation in the same flow.

High uptime on the transactional service, monitored via SLO and real-time alerts
Automated reconciliation — the finance team no longer touches spreadsheets
Simplified sub-acquirer onboarding: merchants open the account and transact the same day
Support for multiple payment methods inside the same SmartPOS checkout flow

Stack

Technologies in production

Kotlin (Android SmartPOS)React NativeNode.jsPostgreSQLApache KafkaAWS KMSPix API (Banco Central)Apple Pay PassKit

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Payments is risk — and margin

If your product needs to embed payments, we deliver the stack and take on the technical risk alongside your team.

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