Senior Software Engineer - Node / React

Simplex.; New York (NY); On-site; USD 180,000 - 220,000; Full time

Benefits offered by this job

Unlimited PTO

Full benefits package

Equity

Job summary

Simplex seeks a Senior Engineer in New York City to strengthen core platform services and user-facing features. The role emphasizes building with a long-term view, writing clean, scalable code, and delivering observable systems in a fintech-enabled environment.

You will work onsite in Flatiron, collaborate closely with product teams, and contribute to architecture decisions, CI/CD, and tooling, with equity opportunities for the right candidate.

Qualifications

• At least 5 years of software engineering experience.
• Strong CS foundation; familiarity with data-intensive architectures.
• Designs extensible APIs and abstractions for long-term maintainability.
• Excellent communication to translate product requirements into technical tasks.
• Hands-on with serverless architectures in cloud environments (e.g., AWS).

Responsibilities

• Build and own new user-facing features end-to-end, from data models to UI components.
• Improve observability: analytics, monitoring, and alerting across systems.
• Collaborate with product and engineering to architect differentiators including embedded fintech and AI agents.
• Develop CI/CD pipelines and developer tooling to increase development velocity.
• Shape engineering processes to support a world-class product.

Skills

Node.js

React

Next.js

TypeScript

AWS

Serverless

Tools

AWS

Terraform

Job description

Our client is a fast-growing, venture-backed technology company that has built a modernized Point-of-Sale (POS) platform purpose-built for a niche industry. Two years in, they have achieved meaningful scale - serving 150+ multi-location enterprise customers with a system that operates around the clock across multiple time zones, acting as the core platform for procurement, transactions, and reporting.

They work fully in-person, 5 days a week, out of their office in the Flatiron district of New York City. Relocation assistance and visa sponsorship are not available at this time.

Who They're Looking For

As a Senior Engineer, you'll be expected to bring strong engineering principles backed by at least 5 years of experience. The ideal candidate:

• Has a strong computer science and programming foundation - has read Designing Data-Intensive Applications
• Is a craftsperson who deeply cares about the quality of their output and understands the long-term costs of shortcuts
• Builds with the end user and longevity in mind - knows how to design abstractions and APIs that are a pleasure for both customers and teammates to use
• Communicates effectively to drive clarity and alignment across the organization - able to translate product requirements into technical challenges and vice versa
• Is genuinely passionate about software engineering and dives deep into topics that interest them, whether that's the Node.js Event Loop or how virtual memory works at the OS level
• Has hands-on experience with serverless architectures - comfortable designing and deploying serverless functions and event-driven systems in cloud environments (e.g., AWS Lambda, Vercel Edge Functions, or equivalent)

What You'll Work On

• Build and own new user-facing features end-to-end, from database models to UI components
• Continuously improve observability across existing systems - analytics, monitoring, and alerting
• Collaborate with product and engineering to architect key differentiators, including embedded fintech products and AI agents to help merchants manage their stores
• Build CI/CD pipelines and developer tooling (e.g., feature environments) that increase development velocity
• Help shape engineering processes to support building a world-class product

Familiarity with every tool isn't required, but candidates should have the foundational knowledge to understand what powers them under the hood:

• Node
• React
• Next.js deployed on Vercel
• Typescript
• AWS (particularly RDS)
• Terraform or equivalent infrastructure-as-code tooling
• Salary: $180K-$220K + meaningful equity, depending on experience
• Unlimited PTO
• Full benefits package: medical, dental, vision, 401(k), transportation, and more

Interview Process

• One or two 30-minute introductory calls with the engineering team
• Onsite interview consisting of:
• 45-minute meeting with the product team and company leadership