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CASE STUDYFINTECH · MULTI PSP PAYMENT AGGREGATOR

bluSwap

A payments aggregator uniting eight PSPs behind one gateway with automated settlements, plus a companion payout and accounting product — both built by a single dedicated engineer.

58Weeks operated
2k+Hours of work
1Engineers

The brief

Build and extend a payments and settlements platform (BluSwap) by onboarding onto the existing codebase, resolving architectural debt (primary key migration, Redis/Celery issues), and progressively adding payment provider integrations, settlement automation, and a parallel payout/accounting product (BluFin360) — all operated by a single Antino developer on a Developers On Demand model.

What we built

Two production-grade fintech platforms built by a single engineer over 58 weeks:

  • BluSwap — a multi-PSP payment gateway aggregator integrating 8 providers (EnKash, NuPay, ApexIO, Mplify, PhonePe, Unlimit, GramePay, Kotak) supporting UPI, QR, card, and direct payment flows with per-merchant revenue/commission/GST calculation, automated settlement reporting, multi-VPA management, async MongoDB audit trail, RBAC middleware, and a checkout/payment-link system
  • BluFin360 — a companion payout and accounting platform with virtual accounts, Kotak bank payout API, double-entry ledger, voucher/journal APIs, tax dashboard, and unified reporting. Both platforms are hardened with PGBouncer, read-replica routing, rate limiting, CloudWatch alerting, and Grafana monitoring.
⊛ Live in production

Both BluSwap (multi-PSP payment routing, settlement reporting, multi-VPA, audit trail) and BluFin360 (payout, ledger, accounting, tax dashboard) are live in production on AWS. Rate limiting, CloudWatch alerting, PGBouncer connection pooling, and DB credential rotation are active. Full KT and documentation were delivered; the Antino engineer has offboarded as of April 10, 2026.

How it was built, phase by phase.

8 workstreams across 58 weeks of operated delivery

  1. (001)DISCOVERWeek 1–2 (Mar 03–Mar 13, 2025)

    Platform Onboarding & Architecture Discovery

    Deep technical KT covering ORM, Redis, Celery, BulkPe, payment gateway architecture, infra understanding, primary key issues, and overall system design review during the first two weeks of engagement.

    ✓ Full architectural understanding established; Redis/Celery issues resolved; foundation set for feature delivery

    RedisCeleryORMBulkPeSlackJira
  2. (002)BUILDWeek 3–5 (Mar 19–Apr 04, 2025)

    Audit Report Generation System

    End-to-end audit report pipeline including transaction data APIs, file generation, S3 storage with encrypted links, PIN-based security, SQS queue integration, email delivery, and query optimization.

    ✓ Fully functional audit report system with secure S3 links, email delivery, and authentication deployed to dev

    AWS S3AWS SQSPython DjangoFastAPICelery
  3. (003)BUILDWeek 6 (Apr 07–Apr 08, 2025)

    RBAC Middleware & Authentication Layer

    Role-based access control system built with custom middleware, decorators, and JWT token decode logic for merchant and admin roles across the platform.

    ✓ Merchant and admin separation enforced across APIs; later extended to BluFin360 subsidiary product

    Python DjangoFastAPIJWT
  4. (004)INTEGRATEWeek 7–26 (Apr 09–Aug 29, 2025)

    Multi-PSP Payment Gateway Integration (EnKash, NuPay, ApexIO, Mplify, PhonePe, Unlimit, GramePay, Kotak)

    Sequential integration of 8 payment service providers covering UPI, QR code, card, intent, and direct payment flows.

    ✓ Full multi-PSP payment routing live in production; platform can route transactions across 8 providers with per-method revenue tracking

    EnKash APINuPay APIApexIO APIMplify APIPhonePe APIUnlimit API
  5. (005)BUILDWeek 11–18 (May 08–Jul 11, 2025)

    MongoDB Transaction Audit Trail (Async Logger)

    Asynchronous MongoDB logging system for full transaction trail capture across PSP callbacks, scheduled status checks, and ApexIO flows — enabling forensic debugging and audit compliance.

    ✓ Non-blocking async transaction trail in MongoDB across all PSP providers, enabling audit and debugging without performance impact

    MongoDBPythonFastAPICelery
  6. (006)BUILDWeek 14–21 (Jun 05–Jul 22, 2025)

    Revenue, Commission & GST Calculation Engine

    Dynamic charge and revenue computation engine supporting per-merchant rate configurations, GST calculation with merchant-specific rules, commission deduction logic, and integration with settlement flows.

    ✓ Configurable per-merchant charge, commission, and GST engine serving live settlement and reporting pipelines

    Python DjangoFastAPIPostgreSQL
  7. (007)BUILDWeek 15–18 (Jun 09–Jul 02, 2025)

    Settlement Reporting & Cronjob Automation

    Automated settlement report generation via Celery cronjobs with T-5min and T-10min checks before settlement cutoffs, mailer integration, decimal correction, and admin reporting APIs.

    ✓ Automated settlement reporting running on schedule with emailed reports and admin-accessible transaction overviews

    CeleryRedisPython DjangoAWS SES
  8. (008)BUILDWeek 21–25 (Jul 24–Aug 01, 2025) + Nov 2025

    Multi-VPA (Virtual Payment Address) Management

    CRUD APIs for merchant VPA management, dynamic VPA allocation, multi-VPA support per merchant, reconciliation against wallet thresholds, and QR/intent generation from bank-provided VPAs.

    ✓ Merchants can operate multiple VPAs; bank-generated VPAs feed checkout QR/intent flows in production

    FastAPIPython DjangoPostgreSQLUPI

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