Senior Software Engineer, Back-End (Payments)

Collectors • Berkeley, CA

2d • $140,971 - $228,870 • Hybrid

About The Position

We are looking for a Senior Software Engineer to join our Payments team — a critical engineering domain responsible for building, scaling, and evolving the payments infrastructure that powers every transaction across the Collectors ecosystem. This team owns the full lifecycle of payment capabilities: integrating with and abstracting across multiple payment gateway providers (including Stripe and PayPal), supporting payment methods spanning credit card, ACH, and digital wallets, and building both the APIs that downstream services depend on and the web application experiences that customers and internal tools rely on. You will work across backend APIs and modern frontend surfaces, partnering with product, design, and cross-functional engineering teams to deliver reliable, scalable, and secure payment experiences. This is a high-impact, high-visibility role. Payments is the financial backbone of our marketplace — touching grading order checkout, vault and consignment transactions, partner payouts, and customer wallet top-ups. You will have direct influence over architecture decisions, gateway integrations, and the quality bar for everything that ships. We believe there is significant value in onsite partnership and team collaboration, and candidates within 1-hour commuting distance of the office may be expected to work onsite most of the time. Additional details will be discussed during the recruiting process.

Requirements

• 6+ years engineering experience.
• You have a track record of designing, shipping, and scaling products that have measurable business impact.
• Ideally 2+ years operating as a Senior IC or equivalent technical leadership level at a high-growth company or a scaled consumer platform.
• Deep backend expertise in C# (.NET). You’re comfortable owning complex API surfaces, async patterns, and data consistency in distributed systems.
• Frontend range in React, Svelte, and TypeScript. You build clean, responsive payment UIs and understand the nuances of state management, form handling, and secure client-side data flows.
• Strong fundamentals working with databases and data modeling, both relational (e.g. PostgreSQL) and NoSQL (e.g. DynamoDB). You're comfortable designing schemas, writing efficient queries, and choosing the right storage layer for the problem.
• Familiar with Agile/Scrum methodologies. You're comfortable working in iterative delivery cycles, participating in sprint planning, and adapting quickly to changing priorities.
• Payments or fintech experience. You understand gateway integrations, idempotency, webhook reliability, tokenization, and PCI compliance in production environments.
• Distributed-systems depth. You’ve designed and operated microservices and Kafka-based event-driven architectures, run workloads on Kubernetes, and know your way around the AWS ecosystem.
• AI-first engineer. You build with AI tooling across the SDLC — from planning and code generation to review and debugging. You have a clear, practiced point of view on how AI raises the quality bar and accelerates delivery.
• Observability-first mindset. You instrument what you ship using Datadog or similar tools. You're comfortable building dashboards, setting up monitoring/alerting, and using distributed tracing to debug production issues.
• Security-minded. You treat payment security as a first-class engineering concern, not an afterthought.
• Influential communicator. A strong written and verbal communicator with sharp analytical and troubleshooting instincts — you align engineers, product partners, and stakeholders without direct authority, make crisp calls, and bring people with you.
• Bias for ownership. You have an extreme ownership mindset and will wear any hat required to get the job done. You thrive in a fast-moving, self-directed environment — you set the bar, hold it, and take full accountability for outcomes.

Nice To Haves

• Passion for collecting is a plus.

Responsibilities

• Build and evolve multi-gateway payment integrations: Design, implement, and maintain integrations with multiple payment gateway providers — including Stripe, PayPal, and others — building clean abstractions that minimize disruption when adding or swapping gateways, while owning payment flows end-to-end from initiation through settlement, refund, and reconciliation.
• Deliver full-stack payment experiences: Develop backend payment services and APIs in C#/.NET while building intuitive customer-facing experiences in React, Svelte, and TypeScript that power checkout and payment management, collaborating closely with design and product to ensure every flow is accessible and conversion-optimized.
• Champion security, compliance, and resilience: Apply PCI-DSS best practices and resilient design patterns — including tokenization, idempotency, retries, and audit controls — to ensure secure and reliable payment processing at scale, partnering with Security and Compliance teams to maintain and advance our certifications.
• Take an AI-first approach to building: Leverage AI-assisted development tools throughout the software lifecycle to accelerate delivery, improve quality, and evolve engineering best practices.
• Architect for scale and observability: Design and operate distributed, event-driven services on AWS and Kubernetes, using metrics, tracing, and alerting to maintain highly availability and accelerate incident response.
• Drive cross-functional execution: Translate business requirements into technical solutions and partner across Payments, Marketplace, Grading, Vault, and platform teams to deliver seamless payment experiences that connect the Collectors ecosystem.

Benefits

• Health Insurance: All full-time employees are eligible to enroll in Medical, Dental, and Vision
• Additional Benefits: Full-time employees are eligible for fertility, commuter, and educational assistance benefits
• 401(K) Matching Plan: We are proud to offer a competitive 401k matching plan to our employees to support their future financial goals
• Vacation: All salaried employees are eligible for flexible time-off
• Holiday Pay: All regular, full-time employees are eligible for ten company paid holidays
• Employee Discounts: Employees receive discounts on select grading services for approved submissions
• Flexible Hours: Many of our teams offer flexible schedules with varying shifts and will work with you to accommodate your needs
• Fun Working Environment: Our team members are invited to participate in celebrations, holiday events, and team building activities

What This Job Offers

• Job Type: Full-time
• Career Level: Senior
• Education Level: No Education Listed