Senior Backend Engineer — Payroll & Ledgers

Simplex Hires LLC; New York (NY); On-site; USD 220,000 - 300,000; Full time

Benefits offered by this job

Fully covered medical & dental

401(k)

Catered lunches and dinners

Job summary

Simplex Hires LLC is hiring for a senior backend engineer to own the payroll and financial systems in our NYC office. You will design double-entry ledgers, idempotent payment execution, and reconciliations that auditors can read, partnering with Platform Engineering and store owners to ensure accuracy across payroll, bills, and deposits.

You will drive the financial-correctness standards, build integrations, and guide the code quality in a small, ownership-driven team that ships rapidly with

Qualifications

• 5+ years building production backend systems.
• Proficient in TypeScript/Node or equivalent languages.
• Practical fluency with transactional guarantees and idempotency.
• Real depth in PostgreSQL including scalable schema design.
• Experience with accounting/financial data and reconciliations.

Responsibilities

• Build payroll and billing components from the ground up with correct, auditable ledgers.
• Own accounting integrations (e.g., QuickBooks) and ensure month-end balance accuracy.
• Design and maintain money-movement rails with robust error handling and retries.
• Collaborate with Platform Engineering and store owners to ensure seamless workflows.
• Establish financial-correctness patterns for other teams to adopt.
• Leverage AI coding agents within safe guardrails for money-touching code.

Skills

Backend development

TypeScript/Node

PostgreSQL

Transactional guarantees

Code quality & reviews

Tools

Next.js

tRPC

Prisma

Vercel

RDS

Job description

Simplex Hires LLC is hiring for a senior backend engineer to own the payroll and financial systems in our NYC office. You will design double-entry ledgers, idempotent payment execution, and reconciliations that auditors can read, partnering with Platform Engineering and store owners to ensure accuracy across payroll, bills, and deposits.

You will drive the financial-correctness standards, build integrations, and guide the code quality in a small, ownership-driven team that ships rapidly with