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Backend · 2025 · Paismo

Paismo — Nexus API & HRMS Platform

Enterprise workforce API and multi-tenant HRMS backend serving payroll, time and attendance, leave, and document generation

Role: Backend Engineer III

Node.jsNestJSPostgreSQLUnified.toNx MonorepoAuth0CASLOpenTelemetryJaegerPrometheusAWS LambdaSQSStripeLaunchDarklyWebSocketsPuppeteer

1,000 req/min

Rate Limit

Nexus API

77

Entity Modules

Fully isolated per tenant

2

Integrations

QuickBooks + Xero live

100%

Audit Coverage

All events logged

The Challenge

  • —No public API existed for enterprise integrations — ERP platforms like NetSuite and SAP and identity providers like Azure AD had no way to programmatically access workforce data
  • —No reporting mechanism existed — admins had no way to generate consolidated employee reports across payroll, attendance, and leave
  • —Employee record changes had no audit trail making compliance and HR traceability impossible
  • —Clients on external accounting platforms had no way to sync data with Paismo without manual exports

Process

  • 01Designed the Reporting Engine from scratch covering payroll, attendance, timesheets, leave balances and deductions in one unified report
  • 02Built Employee Lifecycle module as an immutable audit log — every change to any employee record creates a new history entry
  • 03Architected Synapse Integration as a standalone NestJS microservice in an Nx monorepo with its own deployment boundary
  • 04Implemented OAuth flow, connection management and cron-based scheduler for automatic bi-directional syncs via Unified.to API
  • 05Designed entity mapping tables and snapshot tracking so syncs are resumable and idempotent

The Solution

  • ✓Reporting Engine generating comprehensive monthly reports combining data from all HRMS modules
  • ✓Employee Lifecycle module providing full immutable audit trail meeting ISO 27001 compliance requirements
  • ✓Synapse Integration microservice enabling bi-directional sync between Paismo and QuickBooks and Xero
  • ✓Architecture designed to add new integration providers without rebuilding core sync logic

Architecture

1

Nexus API — Public Enterprise Workforce API

API key plus secret authentication with strict per-tenant data isolation. Helmet security headers, JSON schema validation, and audit logging on every request. Rate limited at 1,000 requests per minute. Webhook system for real-time downstream sync. Built for ERP integrations, identity providers, and workforce analytics platforms.

2

Synapse Integration Microservice

Standalone NestJS service handling all external accounting integrations. Unified.to abstraction means adding a new accounting provider requires zero changes to core HRMS logic.

3

Reporting Engine

PostgreSQL-backed reporting layer with dynamic query generation. HR managers can define report schemas and schedule automated exports without engineering involvement.

4

Employee Lifecycle Module

Covers onboarding, role changes, leaves, and offboarding with state machine-driven transitions. Each lifecycle event emits domain events consumed by payroll, reporting, and integrations.

Takeaways

  • →Built three independent features that became core parts of the Paismo product
  • →Gained deep experience with microservice boundaries, Nx monorepos and event-driven sync patterns
  • →Strengthened understanding of compliance requirements in HR software at scale