Payments Engineer

About Agent Mercer

Agent Mercer connects the systems behind an online business.

We build checkout, payments, subscriptions and agents together, so a business can operate from one connected system.

Our foundation includes payment routing, network tokens, recurring billing and dispute prevention.

The Role

We are hiring a Payments Engineer to own the payment rails at the heart of our platform. You will work directly with the founders and a small senior engineering team on systems that move real money for our customers every day.

This is a senior, high-ownership role. We are looking for an engineer who has built and shipped production payment systems end-to-end, makes sound architectural decisions independently, and brings deep instincts for the edge cases that define payments — declines, retries, chargebacks, reconciliation. You should be comfortable owning entire flows from spec through deployment with minimal oversight.

Responsibilities

• Architect and ship multi-PSP payment routing across nine or more processors using strategy-pattern adapters in NestJS and TypeScript
• Build and maintain network tokenization flows and processor-agnostic token storage at PCI Level 1
• Design and implement subscription billing logic, including CIT checkout, MIT rebilling, authorization holds, captures, refunds, and voids
• Build webhook consumers for asynchronous processor events across all PSPs
• Design retry logic, dunning, and reconciliation flows that maximize approval rates and recover failed payments
• Develop custom checkout experiences supporting credit card, Apple Pay, Google Pay, and PayPal
• Integrate with the Shopify Admin and Storefront APIs for order creation, selling plan management, and merchant onboarding
• Mentor engineers and contribute to engineering best practices

Required Qualifications

• Five or more years of professional software engineering experience, with a track record of shipping production systems end-to-end
• Strong backend engineering skills, with deep experience in Node.js and TypeScript (NestJS or a comparable framework)
• Demonstrated experience integrating payment processors such as Stripe, Adyen, NMI, Airwallex, or Braintree
• Working knowledge of payment tokenization, vaulting, and PCI compliance principles
• Experience with multi-PSP routing or orchestration architectures
• Working knowledge of CIT versus MIT transaction flows, authorization and capture patterns, and webhook event handling
• Deep experience with relational databases, including SQL and PostgreSQL
• Demonstrated ability to operate independently in early-stage or high-velocity environments
• Strong written and verbal communication skills

Preferred Qualifications

• Experience with network tokenization and tokenization platforms such as Basis Theory, Evervault, Spreedly, or VGS
• Experience building checkout flows for Shopify, BigCommerce, WooCommerce, or custom platforms
• Experience with subscription billing platforms such as Stripe Billing, Recurly, or Chargebee
• Familiarity with dispute prevention, chargeback management, and approval rate optimization

Our stack

Backend

NestJS · Node.js · TypeScript

Payment Processors

Stripe (Connect + Billing) · Adyen · Airwallex · NMI · Nuvei · Authorize.Net · Braintree · PayPal

Tokenization & Security

Network tokenization · Processor-agnostic token storage · PCI Level 1

Wallets & Methods

Apple Pay · Google Pay · PayPal · Cards

Commerce

Shopify Admin & Storefront APIs (GraphQL)

Data

Supabase (PostgreSQL)

Tooling

Sentry · Linear · GitHub