Product Case

Nexus
Platform

Ticketing platform with WhatsApp sales, integrated payments, and resilient event check-in operations.

Scope Full-stack · Architecture
Stack NestJS · PostgreSQL · WhatsApp · Mercado Pago
Code Private code (NDA)
KPI 100% offline check-in
Message on WhatsApp ↗ View Evidence Private code (NDA)
Architecture diagram of the Nexus Platform: offline-first PWA, multi-tenant NestJS backend, WhatsApp Cloud API, Mercado Pago, and infrastructure with Redis and Prometheus
System architecture — main flows and infrastructure layers.
01

TL;DR — 1 minute

Problem

Sales and check-in depended on fragmented channels and stable internet at the gate during a critical operation.

Solution

WhatsApp flow + multi-tenant backend + offline-first check-in with a local queue and batch sync.

Result

The gate operates without internet with safe sync and fewer incidents on event day.

Private code (NDA). This software is in production and owned by a company. Access to sanitized material can be requested directly.
02

Snapshot

Role
Full-stack, NestJS + React/Next.
Scale
Multi-tenant, multiple organizations running operations simultaneously.
Constraints
Offline gate operations; idempotency and traceability are mandatory across integrations.
03

Problem & Impact

  • Symptom The gate freezes without connectivity, and operations lose fluency exactly when pressure is highest.
  • Cause Lack of an offline-first mechanism with queue and controlled retry for the critical operation.
  • Impact High operational risk, reprocessing inconsistencies, and increased support on event day.
04

Approach

1
Sales

WhatsApp Cloud API with multi-tenant orchestration to reduce purchase steps and preserve context per organization.

2
Payments

Mercado Pago with admin routes for operations, reconciliation, and support without spreading critical rules across the front end.

3
Offline-first

IndexedDB + batch sync to reduce reconnect spikes and keep the gate usable even without internet.

05

Reliability

Risks

Duplicate retries, reconnect spikes, and operational inconsistency across devices.

Guarantees

Idempotency through externalId and a local queue with controlled retry and batch synchronization.

Evidence

A real snippet of the queue/sync mechanism used in offline operations.

JS · Node.js 
await db.add('syncQueue', {
  url,
  method,
  body,
  timestamp: Date.now(),
  retryCount: 0
});
await fetch(syncUrl, { method: 'POST', body: JSON.stringify({ orders }) });
NestJSPostgreSQLWhatsApp Cloud APIMercado PagoPWAIndexedDB
06

Extensions & Next steps

  • Queue observability: pending items, average age, and synchronization rate.
  • Consolidated operational reports for check-in, POS, and reconciliation.
  • WhatsApp → payment → issuance funnel metrics to identify bottlenecks.
Do you have this problem?

Need low-friction sales and field operations that do not depend on internet?

I design offline-first flows with idempotency, batch sync, and audit trails.

Message on WhatsApp ↗ Private code (NDA) Evidence
Back Top Next case